Piero Scaruffi(Copyright © 2013 Piero Scaruffi | Legal restrictions )
These are excerpts and elaborations from my book "The Nature of Consciousness"
Common sense is a key factor for acting in the real world. We rarely employ classical Logic to determine how to act in a new situation. More often, the new situation “calls” for some obvious reaction, which stems purely from common sense. If we used Logic, and only Logic, in our daily lives, we would probably be able to carry out only a few actions a day. Logic is too cumbersome, and allows us to reach a conclusion only when a problem is “well” formulated. In more than one way, common sense helps us deal with the complexity of the real world. Common sense provides a shortcut to making critical decisions very quickly.
Common sense encompasses both reasoning methods and knowledge that are obvious to humans but that are quite distinct from the tools of classical Logic. When scientists try to formalize common sense, or when they research how to endow a machine (such as the computer) with common sense, they are faced with the limitations of classical Logic. It is extremely difficult, if not utterly impossible, to build a mathematical model for some of the simplest decisions we make. Common sense knows how to draw conclusions even in the face of incomplete or unreliable information. Common sense knows how to deal with imprecise quantities, such as “many”, “red”, “almost”. Common sense knows how to deal with a problem that is so complex it cannot even be specified (even cooking a meal theoretically involves an infinite number of choices). Common sense knows how to revise beliefs based on facts that all of a sudden are proved false. Logic was not built for any of these scenarios.
Furthermore, common sense does not have to deal with logical paradoxes. Paradoxes arising from self-referentiality (such as the liar’s paradox) have plagued Logic since the beginning.
A program to ground common sense in Predicate Logic is apparently contradictory, or at least a historical paradox. Science was born out of the need to remove the erroneous beliefs of common sense: e.g., the Earth is not the center of the universe. Science checks our senses and provides us with mathematical tools to figure out the correct description of the world notwithstanding our sense’s misleading perceptions. Science was born out of the need to get rid of common sense.
What was neglected is that common sense makes evolutionary sense. Its purpose is not to provide exact knowledge: its purpose is to help an individual survive.
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