m.a. wrote:
> *Okay, so is it true to say that things written in EXTENSION are never 
> in formula style but are translated into formulas when we put them 
> into  INTENSION   form?  You can see that my difficulty with math 
> arises from an inability to master even the simplest definitions.    
> marty a.*

It's not that technical.  I could define the set of books on my shelf by 
giving a list of titles: "The Comprehensible Cosmos", "Set Theory and 
It's Philosophy", "Overshoot", "Quintessence".  That would be a 
definition by extension.  Or I could point to them in succession and 
say, "That and that and that and that." which would be a definition by 
ostension. Or I could just say, "The books on my shelf." which is a 
definition by intension.  An intensional definition is a descriptive 
phrase with an implicit variable, which in logic you might write as: The 
set of things x such that x is a book and x is on my shelf.


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