Re: wff's definition

Saurav wrote:
If one wishes, for some reason, to take a set theoretic approach, the wffs of a language L are defined as a subset of the set of strings over the alphabet of L (i.e. finite sequences of symbols of L) as

{P | P is a string over the alphabet of L & for all A( if A is
"wff-closed" P is in A)}

where a set A is "wff-closed" iff

- every atomic formula is in A
- if P is in A then ~P is in A
- if P and Q are in A then so are P & Q, P <--> Q, P --> Q, P \/ Q
- if P is in A and x is a variable then "for all x P" is in A and so
is "exists x P"

Well, can you prove the unique readability from your definition?

Adding parentheses in the definition of "wff-closed", yes.

--
Aatu Koskensilta (aatu.koskensilta@xxxxxxxxx)

"Wovon man nicht sprechen kann, daruber muss man schweigen"
- Ludwig Wittgenstein, Tractatus Logico-Philosophicus
.

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