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Author Topic: On "Necessarily (the number of planets > 7)"  (Read 352 times)

March 13, 2018, 10:36:37 PM
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Since 9 > 7, by substitutivity of identity, Quine says it follows:

Necessarily (the number of planets > 7)

But there are two ways the scope of the definite description can be interpreted:

Necessarily (Ex)(y)((y numbers the planets equ x = y) & x > 7)

Which is false - but that is not a problem.


(Ex)((y) (y numbers the planets equ x = y) & Necessarily (x > 7))

Which is true & is not a problem.

As both Quine and Russell thought names should be replaced by definite descriptions (although Russell allowed logically proper names).
It is not unfair to exclude names from consideration.

This is discussed (a little differently)by Haack - Philosophy of Logics, location 3991 in kindle)
"It is a commonplace that happiness is not best achieved by those who seek it directly; and it would seem that the same is true of the good."
BR, "Mysticism and Logic" in CPBR Vol. 8, p. 48.