Piero Scaruffi

Mind and Matter The Takeover of the Mind No doubt most people feel that their mind is more important than their body. People may be afraid of losing a limb in an accident, but would still prefer that to losing consciousness. A person who is lying in an irreversible coma is considered "technically dead" even if her body is still alive. We don't mind the transplant of an organ, even of the heart; but we would oppose a transplant of the brain: most people would interpret a heart transplant on them as "somebody is giving me her heart"; but they would interpret a brain transplant on them as "I am giving my body to someone else". We can envision a future in which minds will exist without bodies, but not a future in which we would be happy to be bodies without minds. Ultimately, we are our minds, not our bodies. It is likely that this was not always the case. There was probably a time when survival of the body was more important than survival of the mind. The preeminence of the mind is a recent phenomenon. The main goal of our ancestors was probably to protect their bodies from predators and from natural catastrophes. If the body dies, the individual (whatever an individual is) simply dies. Nature grants the body an obvious preeminence over the mind, a preeminence that we have forgotten but that was probably there for a long time during the evolution of the human species. For a long time, the human mind may have been simply a means to achieve the goal of protecting the human body. Nothing more than an evolutionary advantage over other species in protecting the body. Just like some animals have a fur to protect them from cold weather. Then, somehow, that evolutionary advantage became the predominant part of the individual. To the point that we declare "dead" somebody whose body is alive but whose mind is not. There has been steady progress towards turning the tables: the mind has slowly taken over the body, and now we think of an individual as her mind (whereas we still think of a dog as its body, regardless of whether it has a mind or not). Historically, ancient civilizations don't seem to have appreciated how awesome the human mind is, and don't seem to have realized how "low" non-human things are. For example, ancient Greeks believed that the rivers were children of a god. Today, it may sound strange to think of a river as a "living being", because we know that most of its water changes all the time and we know that its water comes from melting snow and rain, and so forth. But isn't that true of humans too? Don't we change cells all the time? Don't we take in energy and matter from outside (as food)? Doesn't a river have a personality? Other than the fact that rivers live far longer than us, it is not so obvious that having a mind makes humans all that different from rivers, as we today believe. The first part of the mystery is why and how minds became more important than bodies. The second part is, in a sense, proof that the mind is a recent accident: we ask ourselves what is the mind (a rather strange question: what am I?). When we ask what is the mind, we implicitly assume that the body is a given. The body is a given and we wonder what the mind is. We don’t take the mind for granted and wonder what the body is and why we have bodies. We are bodies that wonder about their minds, not minds that wonder about their bodies. At some point, minds happened to bodies. And now bodies use their minds to wonder "how did that happen" and "what is my mind". The quest for a rational explanation of the human mind has always started with the task of defining the relationship between mind and matter: is our mind made of matter? Is it made of a different substance? What differentiates the mental from the non-mental? How do our mind and body relate? Is our mind inside our body? Is our mind born with the body? Will it die with the body? Does it grow with the body? These days, having learned quite a bit about the brain and being reassured by countless psychological experiments that our brain is the main entity of the body responsible for our thinking, we are mostly interested in the specific relationship between brain and mind: what is the relationship between the neural and the mental? How does the mental originate from the neural? And, finally, what is in the mind? Dualism And The Mind-Body Debate Historically, two main schools of thought have antagonized each other: "dualism" and "monism". According to dualism, mind and body are made of two different substances. The first and most famous of dualists was the French philosopher Rene` Descartes (17th century), who is credited as starting the whole "mind-body debate". He observed that reality is divided into matter and spirit. These are two different worlds, made of two different substances. He defined what matter is and what mind is: matter is whatever exhibits the property of "extension" (geometric properties such as "size", "shape", etc.) and mind is… "cogito", i.e. thought (a more scientific definition of mind will come later from Franz Brentano). "Res extensa" (things that have an extension) and "res cogitans" (things that think) belong to two separate realms, and cannot be studied with the same tools. This dualism had an enormous influence on future generations. Newton's Physics, for example, is a direct consequence of that approach: Physics studies the realm of matter, and only deals with matter. And such it will remain until the end of the 20th century. Descartes' dualism was a departure from Aristotle's dualism that had ruled for centuries. Aristotle divided things into living and nonliving. Living beings behaved differently and therefore required a different treatment. Descartes realized that living and nonliving matter are, ultimately, the same matter, that obeys the same physical laws. There is "one" physical world for everything. Living matter appears to "behave" because it is more complex. In reality, animals are mechanical automata. The real distinction is at the level of thought. Some beings (and, for Descartes, it was only humans) can think. The difference is not between living and nonliving matter, which are ultimately the same substance, but between matter and mind, which are two different substances. In a sense, Aristotle's philosophy was centered on life, whereas Descartes' philosophy was centered on man. (It will take three centuries to resurrect the idea that animals, too, may have a mind, and therefore return to Aristotle). Descartes also clearly understood that the brain was the seat of the body-mind interaction, although he couldn't quite explain it. Dualists The 18th century British philosopher David Hume was also a dualist, but he pointed out that "mind" is really a set of "perceptions". The self is an illusion. The mind is simply a theater where perceptions play their part in rapid succession, often intersect and combine. The self is like a republic, whose members have an independent life but are united by a common constitution: the republic is one, even if the members (and maybe even their individual constitutions) are continuously changing. The identity of the republic is provided not by its contents, that are continuously fluctuating, but by the causal relationship that holds its members together. Epiphenomenalism The problem with dualism is how mind and body influence each other while being made of two different substances. In the 18th century the Swiss biologist Charles Bonnet attempted to solve the dilemma by introducing "Epiphenomenalism", the idea that the mind cannot influence the body (an idea later borrowed by the British philosopher Thomas Huxley). Bonnet expanded on Descartes' intuition that mind-body interaction must occur in the brain. He then analyzed the brain and realized that mental activity reflects brain activity. Bonnet also expanded on Descartes' intuition that a body is a mechanical device. He simply added that the automaton is controlled by the brain. Different animals have different functioning (an idea that Huxley married to Darwin's theory) but ultimately they are all bodies run by brains in an optimal way to survive and reproduce. Humans, and possibly other animals as well, are also conscious, but consciousness has no role in directing the automaton. Mind cannot influence the body. The mind merely observes the behavior of the body, although it believes that it actually causes it. (Note that "mind" was pretty much synonymous with "consciousness"). "Epiphenomenalism" therefore accepts that mind and body are made of different substances, but the mind has no influence on the body. The brain causes the mind, but the mind has no saying on the brain's work. Mental events have no material effects, whereas material events may have mental effects. Mental events are simply by-products of material events (like smoke is a by-product of a fire but has no impact on the fire). The World Of Ideas Dualists do not doubt that the mind and the brain communicate somehow. But they are faced with the apparently insurmountable task of making two different substances communicate, even though, by definition, those two substances are not supposed to interact. One way out of this dilemma is to assume the existence of an intermediary between the two. For example, the Austrian philosopher Karl Popper and the British neurophysiologist John Eccles posit the existence of a first world (the world of physical bodies), a second world (the world of mental states) and a third world (the world of products of the mind). The second world communicates with both the others. Abstract objects of mathematics, scientific theories and art products are examples of activities that belong to neither the mental world nor the physical world. Mind plays the role of intermediary between the imaginary world (World 3) and the real world (World 1). "Downward causation" operates from World 3 to World 1. The mind is basically an operator that relates abstract objects and physical ones. Interesting things happen in this third world. First of all, objective knowledge belongs to it: the third world evolves through the growth of objective knowledge. Objective knowledge confers a degree of autonomy to the third world. For example, numbers are created by the mind, but then mathematical laws determine what happens to them, regardless of what our minds think and feel. The growth and evolution of objective knowledge obey the same law that drives biological phenomena of survival and evolution (basically, trial and error). Eccles argues that the interaction between the mind and the brain of an individual is analogous to a probability field of Quantum Mechanics. Mental "energy" can cause neural events by a process analogous to the way a probability field causes action. He calls "psychon" the mental unit that transmit mental intentions to the neural units. The British physicist Roger Penrose, one of the leaders in General Relativity, also subscribes to the notion that there exists a separate world of conscious states and that the mind can access that world. But Penrose's "world of ideas" is still a physicist's world: "protoconscious" information is encoded in space-time geometry at the fundamental Planck scale, and our mind has access to them (i.e., is conscious) when a particular quantum process occurs in our brain. The USA philosopher John Searle does not go that far, but he too rejects the idea that the universe can be partitioned into physical and mental properties. After all, things such as "ungrammatical sentences, my ability to ski, the government and points scored in football games" cannot be easily categorized as mental or physical. The traditional "mental versus physical" dichotomy appears to be pointless. A more humble formulation is due to the USA mathematician Rudy Rucker, who believes in the existence of a separate "mindscape". Rucker asks: "Is what you thought yesterday still part of your mind?" The question is not easy to answer if you assume that ideas are part of minds. Rucker's conclusion is that there exists a world of ideas separate from the mental and the physical. Our minds can travel the mindscape that contains all possible thoughts just like our bodies can travel the physical space that contains all possible locations. Minds share the same mindscape the way bodies share the same physical space. We all share the same mindscape, just like we all share the same universe. In particular, the mindscape contains all mathematical objects and mathematicians explore mindscape the same way astronauts explore physical space. Ditto for natural laws and physicists. Mathematical formula and laws of nature have an independent existence of their own. This is, of course, but a new spin on Plato's old world of ideas. Supervenience There exists two main brands of dualism: "substance" dualism (the mind is a different substance altogether from the brain), such as Popper's and Eccles' "interactionism", and "property" dualism (the mind is the same substance as the brain, but comes from a class of properties that are exclusive of the brain), such as "supervenience" theory (Jaegwon Kim, David Chalmers). "Supervenience" is used to express the fact that a domain is fully determined by another domain. For example, biological properties "supervene" (or "are supervenient") on physical properties, because the biological properties of a system are determined by its physical properties. Biological and physical properties of an organism are different sets of properties, but the physical ones determine the biological ones. Nonetheless, one can study only the biological properties and never deal with the physical ones. The Korean-born philosopher Jaegwon Kim applied the concept to mind: mental properties are supervenient on physical (neural) properties. According to Kim, then, the mental is supervenient on the physical just like the macroscopic properties of objects supervene on their microscopic structures. Intuitively this means that mind is to brain what lightning is to electrically charged particles: the same phenomenon, that presents itself in two different ways. Kim's supervenience defines a relationship between mental and physical, and it also defines some constraints. A mental state cannot correspond to two different physical states. Two brains can't be in the same mental state and be in different physical states. Mental states depend on corresponding neural states: any change in mental states must be matched by a corresponding change in physical states. Mental states "are" neural states, the same way that electricity "is" electrons. One can organize nature in a hierarchy, starting with elementary particles and ending with consciousness. At each level some properties apply, but at the immediately higher level some other properties apply. For example, electrons have mass and spin, but electricity has potential and intensity. Chemical compounds have density and conductivity, whereas biological organisms have growth and reproduction. At each level a new set of properties "emerge": for example, the weak force at the elementary particle level, viscosity at the molecular level, metabolism at the biological level, and consciousness at the cognitive level. The British philosopher Charles Dunbar Broad had already showed in the 1920s that the universe is inherently layered and that each layer yields the following layer but cannot explain the new properties that emerge with it. Supervenience takes it for granted that nature works this way, but offers no explanation at why at a higher level we would find electricity instead of, say, "huicity" or "flowixity" (imaginary properties): why and how just those properties? Why and how the mind emerges from the brain? Ultimately, this is the dilemma of "mental causation": how does the brain cause the mind? In general, this is the dilemma of "second-order properties": how do properties at one level cause properties at another level? John Searle (who believes that minds are high-level features of brains) admits supervenience to the extent that it is causal: the same neural states are also the same mental states because the former cause the latter. Searle thus reduces supervenience to causality. But Kim does not impose any causal relationship: the relationship between the mental and the neural is analogous to the relationship between the usefulness of an object and the features that make it useful: those features do not "cause" its usefulness, they "constitute" its usefulness. All facts of the universe depend (and are therefore supervenient) on physical facts, but the nature of such "dependence" is not trivial, according to the Australian philosopher David Chalmers. Properties that are supervenient on the physical world can normally be reduced to it (i.e., explained in terms of it), but consciousness is not truly, completely supervenient on the neural, and therefore it cannot be reduced to the neural. Consciousness is to some extent supervenient on the physical, but (by the nature of its kind of supervenience) it cannot be explained in physical terms. Monism There is an obvious alternative to dualism: monism. According to monism, body and mind (matter and thought) are made of the same substance: "idealists" think that everything is mental, "materialists" think that everything is material. So monism mainly divides into idealism and materialism. But the "one" substance that everything is made of can also be something else than matter or mind. The Dutch philosopher Baruch Spinoza (17th century), for example, believed that only one substance exists, and that "the" substance has two properties: it is conscious and it has extension. Individuals are parts of that substance, which is ultimately God. God is all that exists (he is what is), there is nothing that is not God. The British philosopher Bertrand Russell was also a monist of sort, because he believed that everything in the universe is made of spacetime events which are neither mental nor physical. Idealism According to idealism, mind is the only substance that makes up all of reality. The German philosopher Gottfried Leibniz (17th century) believed that only minds exist. Humans are not the only ones to have minds. Everything has a mind. Even matter is made of minds. Minds come in degrees, starting with matter (whose minds are very simple) and ending with God (whose mind is infinite). Reality is the set of all finite minds (or "monads") that God has created. Everything has a mind. This extreme view of idealism is called "panpsychism". The Irish philosopher George Berkeley (18th century) thought that all we know is our perceptions, and whatever concepts we can build up from them ("esse est percipi"). We cannot directly know that there is an external world. We only know the internal world of our perceptions. When we talk of an object, we talk of what we see, hear, taste, touch, smell: we talk of something that is inside our mind. An object is an experience. The whole universe is a set of experiences. Ultimately, the only thing that exists is the experiences of our mind. In the 1920s the British mathematicians and philosopher Alfred Whitehead proposed that mental life occurs in a field of protoconscious events. His units are similar to Leibniz's monads, but they are limited in time, and therefore better thought of "mental events". Mental life is a sequence of such mental events that occur in this mental space. As brain studies have proved that the senses present us with a fictitious view of the universe, and subatomic Physics has shown that matter is but clouds of floating particles, and Quantum Mechanics has stated that reality is ultimately in the observer's mind, it has become more tempting to embrace idealism. If everything we see and hear is but an illusion, how can we claim that there really are "things" out there? The only thing that we perceive is what the senses fabricate for us. What we call "reality" is the work of our mind. If Physics even predicts that reality cannot be "measured" without an observer (as Quantum Mechanics does), how can we claim that reality exists independent of our mind? The problem with idealism is that one cannot do much more than claim to be an idealist. Once that claim has been made, reality cannot be used to prove it, since reality is a mere illusion of our mind. Everything is an illusion, including the things that one could use to prove this statement right or wrong. Most scientists believe in a milder form of idealism: the senses do fake reality, and reality does need an observer to become what it is, but sensations do relate to an external world and measurements do measure an external world. The senses and the brain simply alter reality so that we can move about and survive in a world that we can comprehend and manage. And Quantum Physics does not forbid reality from existing, it only forbids us from completely perceiving it. Most scientists believe that the reality that we perceive is indeed a fabrication of our mind, but it does correspond to a reality out there, that exists regardless of our mind. Neutral Monism Philosophers have been debating for centuries whether there are two substances or there is only one substance, whether dualism or monism are the right model for the world. Bertrand Russell reached the conclusion that, if there is a substance, it is neither mental nor material, but, best of all, is to assume that there is no substance at all. His ideas have been largely neglected, which is surprising since his ideas are the only ones in the entire philosophy of mind to be truly based on an understanding of Physics. Russell simply took Einstein literally: if space and time are inseparable, if matter is energy, if everything is relative to the observer, then both matter and mind are meaningless oversimplifications of reality. Matter is less material than Newton thought, and the spirit is less spiritual than Berkley thought. Neither truly exists as a substance. They are rather different ways of organizing space-time. What truly exists is "events". I am a cluster of space-time events that sticks together for a little while. The same argument can be seen from the viewpoint of perception. Sensations are both material and mental. A sensation is part of the object that can be constructed out of it. A sensation is part of the mind in whose biography the perception occurred. An object is defined by all the appearances that emanate from the place where it is towards minds. A mind is defined by all the appearances that start from objects and reach it. If we represent the universe as a network of interactions between many objects and many minds, an object is the collection of all its outputs, a mind is the collection of all its inputs. An object is not the generator of such outputs and a mind is not the receiver of such inputs. The difference between matter and mind is simply the "causal" relationships that are brought to bear. There is no substantial difference between matter and mind. They are built out of the same stuff, which is neither material nor mental (it is "neutral"). Materialism According to materialism, instead, mind and body are made of the same substance (matter, as defined by Physics) and the mental can be explained from the physical. This position was first embraced enthusiastically in te 18th century by the French philosopher Julien Offroy de LaMettrie who envisioned the "Homme Machine", the mind as a machine made of matter, and thought as a material process. Unlike dualism, materialism, in all its variants, admits only one kind of substance, and one class of properties. Materialism had its golden age following a paper ("The Mental and the Physical") published by the Austrian philosopher Herbert Feigl in 1958. It was this paper that established the "mind-body problem" at the center of 20th century philosophy, after so many decades of neglect. Dualism and materialism have been the protagonist of the centuries-old mind-body debate. They both have their pluses and minuses, and neither can overcome its minuses in a plausible way. Dualism's plus is that it does recognize the difference between conscious and non-conscious matter; its minus is that it cannot explain how the mind and the brain connect. Materialism's main asset is that it does not need to explain that connection, since the mind "is" the brain; its drawback is that it cannot explain how consciousness arises from non-conscious matter. Behaviorism A position that tried to get rid of the mind versus matter debate is "behaviorism", which deals with mental terms (such as "belief", "hope" and "fear") only to the extent that they are related to behavior. Following the lead from the USA psychologist John Watson, who had already ruled the mental out in the 1920s, behaviorists reject mental states as unscientific, as an annoyance of our language. What matters is only the relationship between disposition to behavior and actual behavior. In particular, in the late 1940s the British philosopher Gilbert Ryle argued that the mind is not another substance but simply a domain of discourse. Ryle took issue with words that refer to mental objects as if they were on the same level of physical objects. In his opinion, they are not. They are merely words used to describe "behavior". The mental vocabulary does not refer to the structure of something, but simply to the way somebody behaves or will behave. The mind "is" the behavior of the body. Physical objects exist, mental objects are merely vocabulary. Descartes invented a myth: the myth of the mind inside the body. A myth which Ryle parodied with the famous expression "the ghost in the machine": we assume that we have a mind, we ascribe a life to our mind, and when we can't find mind in nature we decide that mind is a different substance or property. Behaviorism is not interested in discussing the mind, but simply behavior and disposition to behavior. Sentences about mental states become scientific and meaningful only when they are translated into sentences about actual and possible behavior. For a behaviorist, a person in pain is simply a person who cries and does some other things that we associate with the word "pain". Psychological behaviorism went even further in claiming that all behavior can be explained as stimulus and response relations. Behaviorism was briefly popular but the renewed fight between dualists and materialists quickly eclipsed it. The Age Of Materialism As the mind-body problem became the "mind-brain problem" during the course of the 20th century, materialism begot "physicalism", according to which a mental state "is" a physical state of the brain. Note that the emphasis on the brain is not completely natural: I feel pain in my foot, not in my brain. But progress in neurophysiology has created a fascination with the brain, which some people describe as the most complex thing in the universe. Therefore the emphasis shifted from the body to the brain although there really is no evidence to rule out that the rest of the body does not affect the mind (there is evidence to the contrary). The "identity theory" (the one pioneered by Feigl) states, point blank, that mental states "are" physical states of the brain (just like lightning is "identical" to a stream of electrons). Since it is a little implausible to assume that for every single mental state there is a unique neural state, a variant of identity theory relaxed this constraint: the "token identity theory" (Donald Davidson) does assume that any mental state is identical to a physical state, but the physical state corresponding to a given mental state is not necessarily always the same one (this allows for two people to have the same feeling, or for the same person to have the same feeling twice, without having every single neuron in the same state both times). The most difficult problem for materialism is to explain how the mind, and especially feelings, can arise from material processes: how can electrochemical activities in my brain suddenly turn into the feeling of pain or fear? John Searle has summarized the problem as a paradox: either the identity theory leaves out the mind, in which case it is implausible, or it does not, in which case it is not materialist anymore. The Identity Theory The main issue with any materialistic theory is how the mind (thoughts, feelings) can be explained from what we know of matter. If mind is ultimately matter, then what is it made of and how is it built? How, in other words, can the mental be reduced to the physical? The "Identity theory" was first advanced by the British (albeit Australian residents) philosophers Ullin Place ("Is consciousness a brain process", 1956) and John Smart ("Sensations and brain processes", 1959). They claimed that perceptions and consciousness are physical processes in the brain, just like lightning is a physical process in the air. They went as far as identifying conscious states with brain states. This removes the question of where the mind-body interaction occurs: since conscious states and physical states are the same thing, they don't need to interact. They "behave" together. A desire, for example, is both a conscious and physical state that causes some actions that are both conscious and physical states. As Herbert Feigl put it, mental states and physical states have the same "extension" but different "intension": they describe the same states, but in a different way. Mental idioms and physical idioms are different descriptions of the same states. From the viewpoint of the man of the street, this thesis is difficult to defend, as mental and physical states are "obviously" different (pain, fear, love as opposed to electrochemical processes in the brain). An old philosophical trick, the so called "Leibniz's law", holds that two things are identical if and only if all the properties that apply to the first one also apply to the other one, and viceversa. But the properties of mental states (such as emotions) and the properties of physical states (such as electrical and chemical properties) are obviously different. There are several variants of the identity theory. Instead of limiting the identity theory to consciousness and sensations, the USA philosopher David Lewis ("An argument for the identity theory", 1966) and the Australian philosopher David Malet Armstrong extended it to everything that is mental, not just consciousness and perceptions: all mental states are physical states in the brain, all mental processes are brain processes. Furthermore, mental states have a "causal" role: a mental state (eg, a belief, a desire, a fear) may cause behavior, and it does so because it is a brain state. A mental state (which is a brain state) both is caused by and causes behavior. For example, lightning is not only a physical process in the air: it is caused by that physical process. A mental state is defined by its causal role: what causes the mental state, what behavior the mental state in turn causes, and its relationship with other mental states. Whatever their spin on the identity theory, all these philosophers faced the same problem: how to explain the emotions we feel, which are obviously very different in nature from a piece of matter. The Irreducibility Problem One elegant way of solving the "irreducibility" problem (how mind can be reduced to matter) was devised by the British philosopher Bertrand Russell. He was keenly aware of the inscrutability of matter in general and of brain matter in particular: we cannot know the nature of matter (electrons, gravitational waves and so forth) other than through theories and experiments, but never feel it directly. In particular, we cannot know the processes that occur in our own brain. Russell thought that mind allows us to perceive, at least, some of those processes as they occur in the brain. He made the remark that what a neurologist really sees while examining someone else’s brain is a part of his own (the neurologist’s) brain. The irreducibility of the mental to the physical is simply an illusion: the mental and the physical are different ways of knowing the same thing, the former by consciousness and the latter by the senses. Consciousness gives us immediate, direct knowledge of what is in the brain, whereas the senses can observe (possibly aided by instruments) what is in the brain. In Russell’s theory, the mental is not reduced to the physical, and the traditional preeminence of the physical over the mental is turned on its head: the mental is a transparent grasp of the intrinsic character of the brain. Consciousness is, basically, just another sense, a sense that, instead of perceiving colors or smells or sounds, perceives the very nature of the brain. Anomalous Monism With his "anomalous monism", Donald Davidson aimed at showing that the mental and the neural are not the same thing (while avoiding Descartes’ dualism) and prepared the ground for the "token theory of identity". Davidson's theory of the mind rests on a simple sillogism: At least some mental events interact causally with physical events Events related as cause and effect fall under strict deterministic laws There are no strict deterministic laws under which mental events can be predicted and explained (this the "anomalism" of the mind). This reads like a contradiction, unless we assume that the mind is something else. What this all means is that the physical and the mental realms have essential features that are somehow mutually incompatible: a mental state cannot just be a brain state. There can be no laws connecting the mental with the physical. In other terms, there can be no theory connecting Psychology and Neurophysiology. In the lingo of the identity theory, Davidson claims that the same instance of a mental state may correspond to different neural states at different times; which means that, given a mental state, it is not possible to relate it to a specific physical state. The same event may be both mental and physical, but there is no relationship between the two descriptions. Davidson believes that there is only one substance, a physical substance, and that "token" events are physical. Every mental event is a physical event, but it is not possible to reduce mental properties to physical properties (there exist no "psychopsysical" laws), and therefore, for example, the language of Psychology cannot be reduced to the language of Physics. The mental is ultimately physical, but there is no way to explain a mental event in terms of physical events. The mental domain cannot be the object of scientific investigation. (Ultimately, this is due to the fact that the mental is holistic). The token identity theory came to identify a less strict version of identity theory: more than one physical state may correspond to the same mental state (a mental state can be realized in several different physical states). This would account for the fact that people with widely different brains can be in the same psychological state. This view opened the doors to functionalism. The Age Of Functionalism If a mental state can be realized in more than one physical state, is the physical state important at all? What is it that makes a physical state of the brain also a mental state? "Functionalists" had an answer: it's the "function" it performs in the life of the organism. This function will cause a behavior. The physical state is not important in determining a mental state, but the function is. We call something a "thermometer" if it measures temperature, regardless of whether it is made of plastic or metal: it is the function, not the material, that determines what things are. Likewise, a mind is a mind if it has the function that a mind has, and it doesn't really matter what it is made of. The "function" of something is a combination of the stimuli it processes, the operation it performs and the external behavior it causes. Functionalism (Armstrong, Lewis) is really a special case of token-identity materialism in which a mental state is defined uniquely by the causal relation it bears over behavior and over other mental states. Mental states express, ultimately, causal relations (the occurring of something causes something else to take place). In other words, they ultimately have a function. Never mind what they are made of: mental states have a function and that is what matters. A consequence of this approach is that a mind doesn’t necessarily require a brain: anything that can play the same function is a mind too. Mental states are defined by their function, and they may as well be implemented in a computer or a brain. As a matter of fact, by using a technique inspired by the British mathematician Frank Ramsey, it is possible to translate every sentence containing "unscientific" psychological terms (such as "believe", "desire", etc.) into a more formal sentence (akin to sentences of predicate logic) which only contains causal relations. The mind is simply the location at which these causal relations are carried out. The difference between functionalists and behaviorists is not so clear cut, of course. Basically, behaviorists refused to deal with mental states and focused on behavior, whereas functionalists said that mental states are such because they causes behavior. Functionalism does not deny the existence of mind, actually it extends the possible realizations of mind in nature (it doesn't have to be a brain). Functionalism has an advantage over materialism: there is evidence that different neural circuits cause the same mental states (different people with different brains feel the same emotions, the same person with a changing brain feels the same emotions, a damaged brain tends to repair itself to perform the same chores it was doing before), but materialism entails that a mental state is a direct consequence of a physical state, which could be meant to signify that two different physical states yield two different mental states. Functionalism allows for "multiple realization". Strictly speaking, it doesn't even require that the mental state be realized in a brain: functionalism is only concerned with the "function", not with the thing that performs the function. Since functions must be carried out by a physical entity, functionalism implied some kind of materialism. David Lewis explicitly married the two, materialism and functionalism: every mental state is a physical state, and every mental state is a functional state. The marriage of the two solved two classes of popular paradoxes, the "mad pain" paradox (what if a human was born who is made of flesh like everybody else but his reaction to the feeling of pain is completely different?) and the "android pain" paradox (what if a being made of different stuff reacted to pain the same way humans do?) The whole debate on one or two substances is meaningless: what is relevant is the function, not the substance. A mind can be "implemented" in whatever number of substances, as long as it performs the function of a mind. Computational Functionalism But how do mental states cause physical behavior? This was still the old conundrum of dualism: how do mind and body interact? A possible solution was found by analogy with a device that had become very popular in the 1950s: the computer. The computer implemented the very concept that a substance (the software) can influence another substance (the hardware). Functionalism thus begot "computational functionalism" (Hilary Putnam, Jerry Fodor, Stephen Stich, Ned Block), according to which the mind is a program and the brain is its hardware, and the execution of that program in that hardware yields a result which is the external behavior of the organism. The mind is a symbol processor (just like a computer) and mental states are related to computational states. Another special case of computational functionalism is "homuncular" functionalism (Daniel Dennett, William Lycan), which decomposes the mind into smaller and smaller minds until it reduces to a physical state: a mental process is the product of many lower mental processes, and each of these lower processes is the product of more and more primitive processes. Each lower layer is less "mental" than the previous one. At the bottom of this hierarchy are the neural processes of the brain. The most common critique of functionalism is that it is utterly implausible that objects different from a brain can have a mind. But then (as Chalmers has pointed out) the brain itself, that ugly, messy, sticky mass of gray and white matter, is an unlikely candidate for something so special as a mind. Why should a computer look more bizarre than a brain? Does mind reside in organization or in substance? Or both? The Computational Theory of the Mind The USA philosopher Hilary Putnam held ("Minds and Machines", 1960) that the same mental state may be implemented by different physical states. For example, each person has a different brain, but every person has the same psychological states of "fear", "happiness", etc. Even other animals exhibit some of the same states. Putnam classified mental states based on their function, i.e. their causal roles within the mental system, regardless of their physical structure. Physical states and mental states can even be grouped in different ways. Putnam then suggested that the psychological state of an individual should be identified with the state of a so-called "Turing machine" (basically, with a computer). A psychological state would cause other psychological states according to the machine's operations. Belief and desire would correspond to formulas stored in two registers of the machine. Appropriate algorithms would process those contents to produce action. Putnam’s idea led to a special case of identity theories, the "computational theory of the mind". The "representational theory of the mind", developed by the USA linguist Jerry Fodor, is an evolution of Putnam’s ideas. Fodor argues that the mind is a symbolic processor. Knowledge of the world is embedded in mental representations, and mental representations are symbols, which possess their causal role in virtue of their syntactic properties (i.e., in virtue of how they can be used in "computing" operations). The mind is endowed with a set of rules to operate on such representations. Cognitive life is the transformation of those rules. The mind processes symbols without knowing what those symbols mean, in a purely syntactic fashion. Behavior is due only to the internal syntactic structures of the mind. The symbols used to build mental representations belong to a language of thought, or "mentalese". Such language cannot be one of the languages we speak because the very ability to speak requires the existence of an internal language of representation. Such language is an intrinsic part of the brain and has been somehow produced through evolution. A belief, for example, is realized as a sentence in the language of thought which resides in the belief area of the brain ("I believe that my name is Piero" is implemented in the belief area by the translation in the language of thought of the English sentence "My name is Piero"). This inner language of thought is shared by all creatures capable of "propositional attitudes" (the simplest form of thought, such as beliefs, hopes, fears, desires). Such creatures can then express their representations in whichever human or animal language they happen to speak. Fodor basically offers a solution to the problem faced by dualists: how to connect the mind and the body, mental states and physical states, the desire to do something and the act of doing it. Beliefs and desires are information, represented by symbols, and symbols are physical states of a processor, and the processor is connected to the muscles of the body. When the symbols change, they have an impact on the body, they cause behavior. At the same time, perception results in a change of those symbols. The processor, in turn, may change the symbols because it compacts several of them into a new one (reasoning). Mind and body communicate via symbol processing. Fodor’s computational theory is consistent with those offered by the USA linguist Noam Chomsky in linguistics and by David Marr in vision: the mind as a set of modules that "compute" something based on an innate symbolic capability. Noam Chomsky spoke of "mental organs", to relate their role to the role of physical organs. Each organ carries out a function and communicates the results to the other organs. Fodor generalizes their ideas: the mind is made of genetically-specified modules, each one specialized in performing one task. A module corresponds to a physical region of the brain, and is isolated from other modules. A module receives input only from modules of lower level, never from higher levels (for example, a belief cannot influence the working of a module that analyzes sensory data). Each module generates output in a common format, the "language of thought". Their outputs are input to the central processor, that manages long-term memory and manufactures beliefs. The central processor is the only module that is not domain-specific. Every other module deals with a specific domain. Fodor does not seem to contemplate cognitive growth: the modules are fixed at birth and remain the same throughout the life of the individual. The approach of the Canadian philosopher Stephen Stich is even more purely syntactic: he even rejects the notion that each object of a mental operation must represent something (or stand for something). Stich assumes that cognitive states correspond to syntactic states in such a way that causal relationships between syntactic states (or between syntactic states and stimuli and actions) correspond to syntactic relationships of corresponding syntactic objects. His "mind" is a purely syntactic program. The USA philosopher Ned Block believes that the psychological state of a person can be identified with the physical process that is taking place in the brain rather than the state in which the brain is. A psychological state can then be represented as the operation performed on a machine, i.e. identified with the computational state of the machine, rather than with its physical state. This way the psychological state does not depend on the physical state of the machine and can be the same for different machines that are in different physical states, but in which the same process is occurring. Block has, actually, provided the broadest criticism of functionalism. "Qualias" (sensations that are associated to the fact of being in a given psychological state) are not easily explained in a functionalist view. Take an organism whose functional states are identical to ours, but in which pain causes the sensation that we associate to pleasure ("inverted qualia"), and an organism whose functional states are identical to ours, but in which pain causes no sensation ("absent qualia"): functionalism cannot, apparently, account for either case. Furthermore, functionalism does not prescribe how we can limit the universe of organisms who have mental states. A functionalist might think that even Bolivia's economy, as expertly manipulated by a financier, has mental states. Homunculi The basic picture of homuncular functionalism was given by the USA philosopher Daniel Dennett. One can explain the feelings of mental life from the non-conscious behavior of the physical world by an infinite regression: a mind is made of a number of simpler minds that are made of even simpler minds, and so forth. We eventually reach levels at which the minds are performing very simple tasks, like computing 1+1 or deciding whether a color is dark or light. At that level it is not difficult to accept the idea that those elementary "minds" are physical, non-mental, things, such as brain processes. Just like adding infinitely-small instants eventually yields a finite interval of time, so adding "infinite" levels of homunculi eventually yields a mind. Dennett reduces the mind to a set of cognitive functions, and then each function to simpler cognitive tasks, each time reducing the "intelligence" needed to solve the problem. Eventually this process reaches a level at which problems can be solved with no more intelligence than the one that can be found in a mechanical device. The idea is that, at each level in the organization of a system, the overall behavior of that level is given by the interaction of a set of interconnected components ("homunculi"). The behavior of each component is itself defined by a set of interconnected components. Another USA philosopher, William Lycan, thinks that, besides the low level of electrochemical processes and the high level of psycho-functional processes, nature is organized in a number of hierarchical levels (subatomic, atomic, molecular, cellular, biological, psychological). And each level is both physical and functional: physical with respect to its immediately higher level and functional with respect to its immediately lower level. Proceeding from lower levels to higher levels we obtain a physical, structural, description of nature (atoms make molecules that make cells that make organs that make bodies...). Proceeding backwards, we obtain a functional description (the behavior of something is explained by the behavior of its parts). The "aggregative ontology" ("bottom-up") and the "structured epistemology" ("top-down") of nature are dual aspects of the same thing. The apparent irreducibility of the mental is due to the irreducibility of the various levels. In a similar vein to Dennett's homunculi, the theory of the "society of mind" advanced by the USA computer scientist Marvin Minsky assumes that intelligent behavior is due to the non-intelligent behavior of a very high number of agents that are organized in a bureaucratic hierarchy. The set of their elementary actions and their communications can produce more and more complex behavior, and eventually mental life as we know it. Brains Cause Minds The state of the "mind-body debate" can be appreciated by vivisecting some of its fundamental tenets. Many contemporary philosophers, notably John Searle, would subscribe to the statement that minds are caused by brains. And the notion sounds intuitively true. A closer inspection reveals how unfounded this view is, and how misleading it can be for reasoning on consciousness. The problem is that the sentence is too informal to yield any formal, scientific discussion. First of all, is the brain sufficient for a mind to exist? Can a brain alone yield a mind? We have no evidence whatsoever of a brain that, alone, causes a mind. Without a heart, would the brain cause a mind? Without the blood? Without the oxygen? Without all the nerves connecting to the senses? If somebody were to cut my head off and pull my brain out, I doubt that my brain would still cause my mind to exist. It would still be made of exactly the same matter, but it would not be able to cause a mind anymore. It would be, quite simply, rotting. The same object causes a mind or not depending on whether it is alive or dead. Truth is, we only have evidence of minds contained in bodies, and in living bodies. Therefore, it would be more appropriate to state that "living bodies cause minds". Second, is the brain necessary for a mind to exist? We have no evidence of other (non-brain) things causing minds, but then we have no way of gathering that evidence. There is no way that we can know whether a different type of thing can also cause a mind. There is no way of knowing if an insect is conscious, if bacteria are conscious, if plants are conscious, if crystals are conscious, etc. Therefore, it would be more prudent to say that "at least living bodies cause minds". Which is a far less exciting proposition than "brains cause minds". But the biggest problem is that even the term "brain" needs to be qualified. What is a brain? Is the skull part of the brain? Are the eyes part of the brain? What are the borders of the brain? Where does a nerve stop being part of the brain? Where do we cut off all the nerves, veins and muscles that link it to the rest of the body? At the chin? At the throat? How much can we change in a brain without changing its being a brain? What about other animals? Do cat’s brains also qualify as brains? Do nervous systems of insects also qualify as brains? Does a computer qualify as a brain? Does a crystal qualify as a brain? What makes a brain a brain? If minds are indeed caused by brains, what needs to be present in a conglomerate of neurons for it to become a brain that causes a mind? As a hypothetical Dr Frankenstein adds features to the ball of fibers that he assembled in his laboratory, at which point does that ugly mess become a mind that feels and thinks? The closer we look, the less sure we are of the intuitive statement that brains cause minds. Intentionality In their search for "the" ultimate definition of what is the mind, for the one property that differentiates the mind from anything else, a recurring popular candidate has been what philosophers call "intentionality" (from the Latin "intendo", which means "to point at"). "Intentionality", or in-existence, of an object is a concept originally introduced by the medieval Scholastics. Their "intentionality" bears no relationship whatsoever to the modern English word "intentional". Their intentionality is the property of referring to something else. Mental states have the (apparently) unique property of referring to something else. For example, we are afraid "of" something, we believe "in" something, we know something. Intentionality is the property of being "about" something. "Fearing", "knowing", "believing" are intentional states. If no other natural phenomena exhibit intentionality, then intentionality could be assumed to be the feature that differentiates the mind from the rest of natural phenomena. All this was summarized in 1874 by the Austrian philosopher Franz Brentano in his influential "thesis": all mental phenomena are intentional; no physical phenomenon is intentional; therefore mental phenomena cannot be reduced to physical phenomena; intentionality is what sets apart mental and physical systems. Brentano noted that every mental phenomenon includes something as an object within itself, although the way it is included is not always the same (in love something is loved, in hate something is hated, and so forth). "This intentional in-existence is characteristic exclusively of mental phenomena." Every thought we have is about something: we love, we hate, we believe in, we fear that, we hope that... something. Intentionality comes in different "flavors", also known as "propositional attitudes", and later philosophers focused on four basic ones (belief, desire, hope, know). Brentano's disciple Alexius Meinong (in his 1904 "theory of objects") even went as far as to state that mental states must have their own existence apart from the physical world. My belief in something is realized by a mental state of something that exists although in a different form than the one in which physical objects exist. What Brentano said was that all mental states are "representations" of objects. What Meinong said was that those representations exist apart from the objects they represent. Neither Brentano nor Meinong explained how these "representations" are generated and what they are made of. There can be many consequences stemming from the theory that the mental is intentional. Brentano's conclusion from his thesis was dualism: the mental and the physical are different substances, and intentionality helps us to discriminate them and study the mental. More than half a century later the USA mathematician and philosopher Willard Quine reached a different conclusion: that intentionality is meaningless, because it does not relate to anything physical. Today, Jerry Fodor believes that the mental is intentional, but it can be reduced to the physical. Daniel Dennett thinks that intentionality is simply a "stance", one of the many we can adopt in studying a system. And not everybody agrees that the intentional can only be mental: the USA philosopher Fred Dretske has studied it as a general property of systems. Intentionality and consciousness are the key features of the mind. What is the relationship between them? John Searle says that everything that is intentional is either conscious or potentially conscious. Intentionality would then be an "enabling" feature of consciousness. A system would be intentional before it could be conscious. Still, what makes an intentional feature conscious? Why is intentionality a prerequisite to consciousness? The Intentional Stance Daniel Dennett thinks that the folk concepts of belief and desire define a fundamental aspect of our language: they help us explain the behavior of systems (including ourselves). But he denies that they have any physical existence of their own. In order to explain and predict the behavior of a system one can employ three strategies: a "physical stance", which infers the behavior from the physical structure and the laws of Physics; a "design stance", which infers the behavior from the function for which it was designed (we know when a clock alarm will go on even if we don't know the internal structure of the clock); and an "intentional stance", which infers the behavior from the beliefs and desires that the system must exhibit to be rational. These are simply three different ways of speaking about the same thing. They are more like three different vocabularies, or languages, than three different sets of things. The "intentional stance" is therefore only a particular way of speaking about systems in general, and our mind in particular. "The tree needs water", "The car wants to be washed", and so forth are examples of the "intentional stance". It is another way to describe the state of objects: the intentional stance. The "intentional stance" is merely the set of beliefs and desires of an organism that allow an observer to predict its actions. Belief and desires are not internal states of the mind which cause behavior, but simply tools which are useful to predict the behavior. No system is truly intentional. The beliefs and desires of an organism, and how they affect the organism's behavior, have biological origins. If an organism survived natural selection, the majority of its beliefs are true and the majority of its desires are possible, and the way the organism employs them is the most "rational" (beliefs are used to satisfy the organism's desires). If this were not the case, the organism would not have survived. Intentional systems are rational systems, by definition. Intentionality and rationality are complementary aspects of natural selection. The fact that some intentional systems are also cognitive systems is a detail. Beliefs and desires are, first and foremost, biological products, and have a biological function. Ultimately, these intentional stances are but descriptions of the relationship between the intentional system (e.g., the mind) and its environment. An entire organism can be described by its intentional stance, since it is a product of natural selection. Facts described from the intentional stance can be explained from the design stance, which is in turn grounded in the physical stance. Mind is what we ascribe to objects, including other humans and ourselves, when we use the intentional stance. It is not a different kind of matter or a different kind of property, it is just a way of describing what happens. Intentionality as Representation Fred Dretske’ theory of intentionality resorts to Claude Shannon's and Warren Weaver's theory of information: a state transports information about another state to the extent that it depends on that other state. By the same token, intentionality can be reduced to a cause-effect relationship: each effect refers to its cause. From Dretske’s perspective, the intentional idiom of beliefs and desires can as well be referred to primitive organisms that only have a system of internal structures. However, the relevance to the explanation of the organism's behavior resides in what such structures indicate: they mean something and mean something "to" the organism of which they are part. In other words, Dretske thinks that intentionality is not unique of mental states, but quite ubiquitous in living and even non-living systems. For example, a thermometer refers to the temperature. Having contents is then not unique to the human mind at all. Mental intentional states are actually somewhat limited compared to the intentional states of physical systems, as they miss a lot of information that physical systems would not miss. Paradoxically, the mind distorts the information that is available in the environment. Other systems are more faithful. This argument can be summarized in terms of representations. The elements of a representational system have a content defined by what it is their function to indicate (what the British philosopher Henry Grice used to call "non-natural meaning"). Dretske distinguishes three types of representational systems: Type I have elements (symbols) that show no intrinsic power of representation (this includes maps, codes, etc); Type II have elements (signs) that are causally related to what they indicate (includes gauges); Type III (or natural) have their own intrinsic indicator functions (unlike Type I and Type II, in which humans are the source of the functions) and therefore a natural power of representation. From this ideas Dretske developed a full-fledged theory of behavior. The term "behavior" is used in many different ways to mean different things. The behavior of an animal is commonly taken to be the actions it performs more or less by instinct or by nature. This is not necessarily "voluntary" behavior. The fact that women have menstruation is part of "female behavior", but it is not voluntary. Behavior is pervasive in nature, and cannot be restricted to animals: plants exhibit behavior too. Behavior is the production of some external effect by some internal cause. Behavior is a complex causal process wherein certain internal conditions produce certain external movements. First and foremost, behavior is a process. A process is caused by both a triggering cause (the reason why it occurs now) and a structural cause (the reason why the process is the way it is). This holds both for human behavior and the behavior of machines (a thermostat turns on a furnace both because the temperature fell below a threshold and because it has been designed to turn on furnaces under certain conditions). In general, humans are interested in structural behavior, which in plants and animals has been determined by natural evolution and in machines has been built by humans. In Dretske’s view, intentionality is not a property useful to differentiate minds from matter, but a property that can help formalize the behavior of systems, both human, biological and mechanical. Phenomenology In 1900 the German philosopher Edmund Husserl had expanded on Brentano's notion of intentionality. Since intentionality links mind and phenomena, he had concluded that phenomena and being are the same thing. In the 1960s, the German philosopher Martin Heidegger, a follower of Husserl's "phenomenology", pointed out a fundamental flaw in dualist theories, and, consequently, in the whole mind-body debate. In his opinion, Descartes' dualism is simply a consequence of a misleading vision of the world, according to which on one hand we have the "objective" world of "physical" reality (made of objects with physical properties) and on the other we have the "subjective" world of "mental" life (feelings, cognition, consciousness). According to this vision, the physical world is described by some objective facts that do not depend on our existence. We can perceive those facts and think about them. And we can act in the world based on our thoughts. But our relationship to the world and its objects is detached, observer-like. Heidegger reminded us that, instead, we are part of that world. We are one of its "objects". We don't exist as independent entities, we exist as part of the world. There is no way that we can step back and, in a detached manner, watch what is happening: we are part of what is happening, and usually it is happening so fast that we don't even have time to think about it. We only have time to react by instinct. Heidegger denies any value to the expressions "physical reality" and "mental life", and to the dichotomy objective/subjective: the world and the mind cannot be separated. Everything is subjective, or objective (depending on the definition), as everything that we know is our "interpretation" of what is happening in the world and we have no way of having an "objective" interpretation of that happening because we are part of it. In our daily life we do not adopt a detached, logic approach to situations but we just "act". Usually, you analyze one of your actions only "after" you have performed it; and, typically, this happens only when something went wrong: you pause to reflect and analyze what and why went wrong. Most of the time we are not "conscious" of why we are doing what we are doing. Heidegger claimed that we are "thrown" into the world. Normally we don't "break down" the situation: we "break down" the world around us only when our actions fail and we need to find out why. For example, we don't normally realize consciously what tools we are using to perform an action: a pair of scissors or a glass or a clutch stick. Only when our action fails, do we focus on the tool that we are using and why it is failing us. When we are hammering a nail into wood, we are not interested in discussing the properties of the hammer and the nail and the wood: we just hammer. If it doesn't work, then we stop and analyze what is wrong with the hammer, the nail or the wood. Same with the objects that surround us: we are rarely aware of every single object that surrounds us. But let's say that somebody locked us in a room and we needed to find a way out of there: only then would we "break down" the reality of that room into all of its objects, desperately looking for some help. Sometimes when you suddenly focus on the drive to work, you get lost: all of a sudden, you don't recognize anymore the streets that you drive through every single morning. There are so many details that you never noticed: was there really a curve? is there really a billboard in that curve? And so forth. But if you don't focus on the route, you know perfectly well how to get to work. If you close your eyes, you have to rediscover your own room, so many details of which are actually unconscious to you, even if you know it better than any other place in the world. When you try to move around your room blindfolded, you "break down" your knowledge about the room. The last time you had to do that was when you moved in. In everyday life, we do not have a complete representation of the situation, and we cannot predict all the consequences of our actions; and we do not have time to search for either the representation or the prediction. Nonetheless we understand a situation and we act in it. And most of the times we survive. Only when our actions fail, do we need to step back and analyze the situation and try to figure out rationally why we failed. Logic is something that we use "after" the fact, to "troubleshoot" what we did wrong. The science that we built to analyze the world is a complication. The truth is much simpler and so closer to our ordinary life. According to Heidegger, there is a fundamental unity of the "Dasein" (of being). Subject and object cannot be separated. They cannot exist independently. An individual is not a separate entity but a manifestation of Dasein in a world and within a tradition (society is a big component of that world). We cannot study out beliefs as objects because we cannot abstract from them and observe them objectively. They are part of our belief system and every action we perform is affected by that same belief system, so we enter a vicious circle. We carry a burden of experience and knowledge with us which shapes our actions. When we study something rationally, in a detached way, we are actually missing something by isolating it. Understanding something is being part of it. Cognition is praxis. We are "thrown" into the world and that's how we understand it and act in it. If we stop and observe it, then we may not be as good at acting in it. Therefore Heidegger does not need mental representations to reason about. What matters is action: action of the world and action of us in the world. Representation is interpretation. There is no "objective" fact (or absolute truth) about the world. Variants on Materialism The problem that has been haunting the endeavors of materialists for centuries is how the mental arises from the physical, how feelings originate from inanimate matter. A modern view is that the mind is indeed material, but somehow its material constituents behave differently from the matter that Physics has explained. Therefore, it is Physics that must be changed, or enlarged, to accommodate new types of natural phenomena. John Searle's position summarizes several of these materialistic opinions. He thinks that (1) the mental is caused by neural processes and (2) the mental is a feature of the brain. Mental states are nonphysical, but form a novel class of features of the brain. Mental phenomena are irreducible to traditional Physics and Chemistry. Their properties (such as meaning and awareness) are different from those of matter. The relation between brain states and mental states is causal, in both directions, each causing the other. Searle calls this relationship between brain and consciousness "non-event causation". Consciousness is an emergent property of the brain in the same way that properties of liquids emerge from those of the molecules they are made of. In other words, the mind is material, but at the same time it cannot be reduced to any other physical property. The British philosopher Galen Strawson is a materialist of sorts. Strawson rejects "neobehaviorism", the view that mental life is linked to behavior in such a way that behavior is essential to the explanation of mental life. He contrasts neo-behaviorism with his own "naturalized Cartesianism", which rests on two assumptions: the mind is physical; the only mental phenomena are the ones that make up our conscious experience (the experiential phenomena). Therefore, representations and intentionality are downgraded to side effects. Eliminative Materialism "Eliminative materialism" is the doctrine that mental states do not exist, or, at least, that the terminology of the mental is wrong and should be abandoned. The German philosopher Paul Feyerabend ("Mental events and the brain", 1963) and the USA philosopher Richard Rorty ("Mind-body identity", 1965) denied the existence of the mental. They claimed that sensations are not brain processes, but the things that we think are sensations are indeed brain processes. The mental is nothing more than a myth. As the USA neuroscientist Paul Churchland puts it, the mental is the subject of "folk psychology", and folk psychology is not a science. Churchland argues that our introspection cannot be trusted as our other senses (such as sight and hearing) mislead us about the real structure of the universe (we don’t see or hear elementary particles and probability waves). It is only the vocabulary of our "folk psychology" that refers to beliefs and desires, sensations, emotions, thoughts, etc. We explain people's behavior by using this terminology, which ascribes mental states to people. In reality, only brain processes exist. In his opinion we should replace the outdated language of folk psychology with the language of neurobiology, just like folk physics was replaced by the more precise language of Newton's Physics. Terms such as "belief" and "desire" are as scientific as the four spirits of alchemy. Churchland points out evidence that folk psychology is unscientific: 1. it has remained the same since the ancient Greeks (but so did Arithmetic, didn't it?); 2. it does not integrate well with the natural sciences (but it has been integrated with computer science by computational functionalism); 3. it is incomplete, as its vocabulary does not apply well to mental phenomena such as sleep and mental diseases (Newton's Physics was also incomplete, but that does not mean that the terminology of mass and energy should be abolished). Churchland denies any validity to "first person" mental life, to consciousness, the self, emotions, etc. He grounds his objection to the fact that there is nothing in the brain that resembles what folk psychology talks about: there are only patterns of neural activity ("activation vectors"). The Cognition-consciousness Problem The distinction between mind and body was clear in Descartes' times, but it is getting less obvious by the day as the physical and psychological sciences shed light on "mental" processes. Several of these processes are not exclusive of the mind (let alone of the human mind), but quite pervasive in nature. Remembering, learning, communicating are, to some extent, present in all forms of life. Since Descartes, the dilemma has been how do body and mind communicate. But, today, there is no mystery in how, say, learning communicates with the body: learning is a brain process that alters brain configurations in such a way that a different behavior will occur. Today, we know that "body" extends to the brain, and brain is responsible for many phenomena that we consider mind and that are no more mysterious than the movement of a hand. Therefore, within the Cartesian dichotomy, "body" must be enlarged to encompass brain processes and "mind" must be restricted to conscious experience. Otherwise, most of the mystery is not a mystery at all: the way "mind" remembers or learns is no more mysterious than the way a muscle gets stronger or weaker. What is mysterious is that "remembering" and "learning" are sometimes associated with conscious experience. That is the real puzzle: how does a brain process of remembering (that is ultimately an electrochemical process of neurons triggering each other) communicate with our conscious life of feelings and emotions that seems to be located in a completely different dimension? As David Chalmers pointed out, the paradox to be explained is not that body and mind communicate but that cognition and consciousness communicate. Mind or Matter It used to be a simple question: what is the soul? "Mind" complicated the question because it related the soul to a specific place, the brain, without being as specific. Is mind the soul? Is mind more than the soul? Is mind less than the soul? The author of this book thinks that the problem is simply formulated in a nonscientific way. "Mind" is a generic term that refers to the set of cognitive faculties we humans have and sometimes (depending on the speaker) it also encompasses consciousness. It would be more appropriate to focus on cognition itself. While some may be reluctant to credit animals with a mind, most will have no problem crediting them with some degree of cognitive faculties, such as memory, learning and even reasoning. Cognition can safely be assumed as a property of at least all living organisms, but a property that comes in (continuous) degrees: humans have "more" of it than, say, snails. Furthermore, there are striking similarities between the behavior of cognitive (living) matter and the behavior of non-cognitive (inanimate) matter. Even a piece of paper exhibits a form of memory that resembles the way our memory works: if you bend it many times in the same direction, it will progressively "learn" to bend in that direction; if you stop bending it, it will slowly resume its flat position. Any piece of matter "remembers" what has happened to it in its shape, and sometimes in its chemical composition (that laboratory scientists can sometimes trace back in time). Far from being unique to the mind, cognitive faculties appear to be ubiquitous in nature. Memory and learning can therefore be said to be ubiquitous in nature, as long as we assume that they come in degrees. Cognition may not necessarily be an exclusive property of living matter. Cognition may be a general property of matter, that the human brain simply amplifies to perform very interesting actions. At least that part of the mind, the one that has to do with cognitive faculties, may be "reduced" to material processes after all. The other part, consciousness, is a vastly more difficult topic. The Factory of Illusions "Thought" is an entirely different game. "Mind" defined as the totality of thoughts is a far more elusive mystery. The mind is a factory of illusions. It creates an inner reality, as opposed to the outer reality of the world. We see colors and shapes, smell odors and perfumes, hear voices and sounds. We perceive the flowing of time. But the universe is made of particles and waves. The mind translates the world into sensations. Then it elaborates sensations to produce thoughts, memories, concepts, ideas. None of this is real. It is all one gigantic illusion. We will never even be sure whether anything exists at all. Then the mind creates consciousness, i.e. the awareness of feeling those sensations and, among them, the subjective sensation of existing. May consciousness be the direct consequence of the existence of those illusions? Are all living beings equipped with sensory perception also endowed with consciousness? Science needs crisp, reliable definitions, especially definitions of the objects it studies. Unfortunately, our mind is one of those things that we intuitively, "obviously" know, but, when we try to formalize, we realize we don’t know at all. The most common way to define the mind is to list cognitive faculties: the mind is something that is capable of learning, remembering, reasoning, etc. The truth is that, by doing so, we have only shifted level: we now have to define learning, remembering, reasoning, etc. The more scientific we try to be, the more we end up with definitions that are broader than we would want them to be. As we saw, many things (and certainly many biological systems) can be said to be capable of some form of learning, remembering, reasoning, etc. Crystals exhibit sophisticated processes of self-organization. What is so special about the mind? It is not the cognitive faculties. It is the inner life. The mind is a factory of illusions, that translates this world of particles and waves into a world of colors, sounds and smells. And it is the illusion of all illusions: consciousness. Therein lies the secret of the mind. Further Reading Armstrong David Malet: A MATERIALIST THEORY OF THE MIND (Humanities Press, 1968) Armstrong David Malet: THE NATURE OF MIND (Cornell Univ Press, 1981) Armstrong, David Malet: THE MIND-BODY PROBLEM (Westview, 1999) Bechtel William: PHILOSOPHY OF MIND (Lawrence Erlbaum, 1988) Block Ned: READINGS IN PHILOSOPHY OF PSYCHOLOGY (Harvard Univ Press, 1980) Bonnet, Charles: ESSAI DE PSYCHOLOGIE (1754) Brentano Franz: PSYCHOLOGY FROM AN EMPIRICAL STANDPOINT (1874) Broad Charlie Dunbar: MIND AND ITS PLACE IN NATURE (1929) Chalmers David: THE CONSCIOUS MIND (Oxford University Press, 1996) Chomsky Noam: LANGUAGE AND THOUGHT (Moyer Bell, 1991) Churchland Paul: MATTER AND CONSCIOUSNESS (MIT Press, 1984) Crane, Tim: THE MECHANICAL MIND (Penguin, 1995) Davidson Donald: INQUIRIES INTO TRUTH AND INTERPRETATION (Clarendon Press, 1984) Dennett Daniel: CONTENT AND CONSCIOUSNESS (Routledge, 1969) Dennett Daniel: KINDS OF MINDS (Basic, 1998) Descartes Rene`: PRINCIPIA PHILOSOPHIAE (1644) Dretske Fred: KNOWLEDGE AND THE FLOW OF INFORMATION (MIT Press, 1981) Dretske Fred: EXPLAINING BEHAVIOR (MIT Press, 1988) Eccles John: EVOLUTION OF THE BRAIN (Routledge, 1991) Eccles John: THE SELF AND ITS BRAIN (Springer, 1994) Feigl Herbert: THE MENTAL AND THE PHYSICAL (Univ of Minnesota Press, 1967) Fodor Jerry: LANGUAGE OF THOUGHT (Crowell, 1975) Fodor Jerry: REPRESENTATIONS (MIT Press, 1981) Fodor Jerry: MODULARITY OF THE MIND (MIT Press, 1983) Fodor Jerry: THE ELM AND THE EXPERT (MIT Press, 1994) Gardner Howard: MIND'S NEW SCIENCE (Basic, 1985) Gregory Richard: OXFORD COMPANION TO THE MIND (Oxford, 1987) Heidegger Martin: BEING AND TIME (1962) Hume, David: A TREATISE OF HUMAN NATURE (1739) Husserl Edmund: LOGICAL INVESTIGATIONS (1900) Kim Jaegwon: SUPERVENIENCE AND MIND (Cambridge University Press, 1993) Kim Jaegwon: MIND IN A PHYSICAL WORLD (MIT Press, 1998) Leibniz: THE MONADOLOGY (1714) Lewis David K.: PHILOSOPHICAL PAPERS (Oxford Press, 1983) Lewis David K.: ON THE PLURALITY OF WORLDS (Basil Blackwell, 1986) Lycan William: CONSCIOUSNESS (MIT Press, 1987) Lycan William: MIND AND COGNITION (MIT Press, 1990) McGinn Colin: CHARACTER OF MIND (Oxford Univ Press, 1997) Popper Karl & Eccles John: THE SELF AND ITS BRAIN (Springer-Verlag, 1977) Popper Karl: KNOWLEDGE AND THE BODY-MIND PROBLEM (Routledge, 1994) Priest, Stephen: THEORIES OF THE MIND (Houghton Mifflin, 1991) Putnam Hilary: MIND, LANGUAGE AND REALITY (Cambridge Univ Press, 1975) Rosenthal David: NATURE OF MIND (Oxford University Press, 1991) Rucker Rudy: INFINITY AND THE MIND (Birkhauser, 1982) Russell Bertrand: ANALYSIS OF MIND (1921) Russell Bertrand: ANALYSIS OF MATTER (Allen and Unwin, 1927) Russell Bertrand: AN INQUIRY INTO MEANING AND TRUTH (Penguin, 1962) Ryle Gilbert: THE CONCEPT OF MIND (Hutchinson, 1949) Searle John: THE REDISCOVERY OF THE MIND (MIT Press, 1992) Sterelny, Kim: THE REPRESENTATIONAL THEORY OF MIND (Blackwell, 1990) Stich Stephen: FROM FOLK PSYCHOLOGY TO COGNITIVE SCIENCE (MIT Press, 1983) Stich Stephen: DECONSTRUCTING THE MIND (Oxford Univ Press, 1996) Whitehead Alfred: THE CONCEPT OF NATURE (Cambridge Univ Press, 1920) Wittgenstein Ludwig: PHILOSOPHICAL INVESTIGATIONS (Macmillan, 1953)