On Sep 13, 11:47 pm, Youness Ayaita <[EMAIL PROTECTED]> wrote:

> I see two perfectly equivalent ways to define a property. This is
> somehow analogous to the mathematical definition of a function f: Of
> course, in order to practically decide which image f(x) is assigned to
> a preimage x, we usually must know a formula first. But the function f
> is not changed if I do not consider the formula, but the whole set
> {(x,f(x))} instead, where x runs over all preimages.
> Concerning properties, we normally have some procedure to define which
> imaginable thing has that property. But I can change my perspective
> and think of the property as being the set of imaginable things having
> the property. This is how David Lewis defines properties (e.g. in his
> book "On the Plurality of Worlds").
> If you insist on the difference between the two definitions, you may
> call your property "property1" and Lewis's property "property2".- Hide quoted 
> text -

Surely you are just talking about the well-known distinction between
intensional and extensional definitions:


"An intensional definition gives the meaning of a term by giving all
the properties required of something that falls under that definition;
the necessary and sufficient conditions for belonging to the set being


"An extensional definition of a concept or term formulates its meaning
by specifying its extension, that is, every object that falls under
the definition of the concept or term in question."

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