[Phil-logic] Substitutability

[Torkel Franzen]

Sandy Hodges says:

 >(T') Any sentence is true if, and only if, it says something and what it says
 >is the case, provided any sentences mentioned by the sentence are normal.

  I don't see how (T') could be called "meaningless", since it's formulated
in ordinary language and is discussed and applied in various contexts.
However, like most things, perhaps, that are said in philosophy, it's
highly unclear and open to various interpretations; whether or not it is
applicable in a particular case is often uncertain, and so on. So I'm
unable to regard the Liar as a deduction of a contradiction from any
apparently correct, or even obvious, principles.