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# Functions from Things to Concepts of them

While the relation denotes(X,x) between concepts and things is many-one, functions going from things to certain concepts of them seem useful. Some things such as numbers can be regarded as having standard concepts. Suppose that Concept1 n gives a standard concept of the number n, so that

We can then have simultaneously

and

(We have bravely used Knew instead of Know, because we are not now concerned with formalizing tense.) (31) can be condensed using Composite1 which takes a number into the proposition that it is composite, i.e.

getting

A further condensation can be achieved using Composite2 defined by

letting us write

which is true even though

is false. (36) is our formal expression of ``Kepler knew that the number of planets is composite'', while (31), (33), and (35) each expresses a proposition that can only be stated awkwardly in English, e.g. as ``Kepler knew that a certain number is composite, where this number (perhaps unbeknownst to Kepler) is the number of planets''.

We may also want a map from things to concepts of them in order to formalize a sentence like, ``Lassie knows the location of all her puppies''. We write this

Here Conceptd takes a puppy into a dog's concept of it, and Locationd takes a dog's concept of a puppy into a dog's concept of its location. The axioms satisfied by Knowd, Locationd and Conceptd can be tailored to our ideas of what dogs know.

A suitable collection of functions from things to concepts might permit a language that omitted some individual concepts like Mike (replacing it with ) and wrote many sentences with quantifiers over things rather than over concepts. However, it is still premature to apply Occam's razor. It may be possible to avoid concepts as objects in expressing particular facts but impossible to avoid them in stating general principles.

Next: Relations between Knowing What Up: FIRST ORDER THEORIES OF Previous: Knowing What and Knowing

John McCarthy
Sun Mar 10 22:57:10 PST 1996