Synopsis:
- Phenomena exist only insofar as the mind perceives them as ideas
- The ultimate reality (the thing-in-itself, "ding an sich") cannot be experienced by the human mind
- We experience the world as we perceive it through our (human) nature
- We cannot know how things are in themselves
- We cannot know the objects of the world, but only our perceptions of such objects
- Idealism
- There exists a thing in itself..
- _but it is unknowable to us
- The empirical world is my representation
- Causality is a relation among representations, not between them and something else
- Space, time and causal relationships are not features of reality in itself
- All our concepts derive from some a-priori knowledge ("trascendentalist idealism")
- A-priori knowledge includes categories of quantity (unity, plurality, totality), categories of quality (reality, negation, limitation), categories of relation (substance-and-accident, cause-and-effect, reciprocity), and categories of modality (possibility, existence, necessity)
- Anything that we experience is located by our mind in space and time and is classified by our mind within those categories
- Space and time pre-exist, but only in our mind
- Knowledge is in our mind, and therefore everything that we know is in our mind (space, time, objects)
- The qualia of an object (color, smell) are not in the object but in our mind, they are manufactured by the perceptive subsystem of our mind
- One cannot "infer" the existence of objects (as Descartes had done)
- The primacy of intuition
- A-priori knowledge is indispensable to perception
- Experience involves processing sense-data (applying a-priori categories to perceptions)
- The human mind is an active originator of experience rather than just a passive recipient of perception
- Perceptual input must be processed, i.e. recognized, or it would just be noise
- Knowledge depends on the structure of the mind
- It is this process of "recognizing" perceptions that generates consciousness (the self)
- Analytic proposition: the predicate is logically contained in the subject (its negation would be meaningless)
- Examples: "Every thing has a size", "Americans are people"
- Truth is self-evident once the concept is analyzed
- Knowledge is not increased
- Synthetic proposition: their truth is not self-evident
- Examples: "My car is white", "This room is large"
- Truth is based on experience of the world
- Knowledge is increased
- Empirical proposition: their truth depends on perception
- Example: "My car is white", "Rob is American"
- A-priori proposition: their truth does not depend on perception (all analytic propositions are a-priori)
- Example: "God exists"
- Synthetic proposition: their truth is not self-evident
- A-priori proposition: their truth does not depend on perception
- Synthetic a-priori propositions: their truth is not dependent on reality, but only on intuition ("2+2=4", "A straight line is the shortest distance between two points", "Every event has a cause"), they could be denied without logical absurdity although we consider them "true" (e.g., non-Euclidean geometry)
- All mathematical propositions are synthetic a-priori: they depend on intuition (they apply a-priori concepts to space and time, which are also a-priori):
- Intuition is of a "spatial" kind in geometry (judgements of geometry are about the structure of space)
- Intuition is of a "temporal" kind in arithmetic (judgements of arithmetic are about the structure of space)
- Physics is made of synthetic a-posteriori (empirical) propositions but also uses synthetic a-priory propositions (e.g., that one event causes another event), which apply a-priory concepts such as causality
- Each category implies a corresponding principle of Physics
- Analytic and a-priori: ok (Analytic and empirical: no)
- Synthetic and empirical: ok (Physics)
- All propositions of Physics constitute synthetic a-posteriori (empirical) judgements: they are indefinitely revisable
- Synthetic and a-priori: can we increase our knowledge independently of experience?
- Kant's thesis: Yes (transcendentalism). Synthetic and a-priori judgments are possible (Physics can yield new knowledge)
- Knowledge consists in categorizing perceptions
- Leibniz: all propositions are analytic, even empirical ones (all empirical propositions can be shown to be logically necessary)
- Hume: only analytic a-priori and synthetic empirical, but no synthetic a-priori propositions
- A synthetic a-priori judgement is one that is true not because
- 1. experience
- 2. the predicate is logically contained within the subject
- It can be proven true via a "transcendental argument", which is a set of methods to use the mind's own functioning to increase the mind's own knowledge. Example:
- "There are objects that exist in space and time outside of me"
- Proof: It would not be possible to be aware of myself as existing without presupposing the existence of something permanent outside of me to distinguish myself from
- Synthetic a-priori knowledge:
- "The amount of energy is always conserved"
- "The angles of a triangle always add up to 180 degrees"
- Physics is valid (Hume claimed it is not)
- Kant's psychology:
- Senses perceive objects (particulars)
- Thought handles concepts (universals)
- Synthetic propositions are applications of a concept (universal) to an object (particular)
- Concepts are:
- a-posteriori/empirical concepts (abstracted from perceived objects),
- a-priori concepts or "categories" (not abstracted from objects, but still applicable to objects),
- ideas (neither abstracted from nor applicable to objects)
- Kant's psychology:
- Synthetic a-priori propositions are applications of categories (a specific kind of concepts) to the perceived objects
- The subjective universe of perceived objects is transformed into the objective universe of causally-linked physical objects by the application of categories to perception
- A chaotic senseless universe of disconnected events is turned into an ordered, meaningful universe of connected events
- It is the thinking being who creates this ordered, meaningful reality (by means of the categories)
- Kant's psychology:
- Ideas are due to an infinite series of deductive inference (why? why? why?_)
- There are only three and they originate
- Psychology (what is the soul?)
- Cosmology (what is the world?)
- Theology (what is God?)
- Ideas cannot be applied to experience
- Categories can only be applied to perceptions
- Applying categories to non-perceived (abstract) ideas leads to an antinomy (a thesis and its antithesis can both be proven true), the domain of metaphysics
- Antinomies can both be proven true:
- 1. "The world has a beginning in time and is limited as regards space" and "The world has no beginning and no limits in space"
- 2. "Every complex substance is made of simple parts" and "Nothing is composed of simple parts"
- 3. "Humans have free will" and "Humans have no free will"
- 4. "There exists a necessary being (God) in the world" and "There does not exist a necessary being (God) in the world"
- The domain of the thesis is the mental world, the domain of the antithesis is the spatiotemporal world
- Kant's Ethics:
- There is an absolute good
- The existence of morality is as evident as the existence of physical objects
- Categorical imperative: good actions are those that one would want as universal laws
- Proofs of God are flawed (they apply an idea to experience, as if it were a category)
- The only evidence of God is that there is no justice (reward proportional to virtue) in this world, therefore there must be an afterlife
- Reason is the final authority for morality ("choose your action as if the principle guiding your action were to become a universal law")
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- Georges Buffon (1789)
- Earliest western account of the history of life and of the Earth that was not based on the Bible
- Newton's natural forces to explain natural phenomena
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