Combining Texts

Ideas for 'On the Question of Absolute Undecidability', 'Appearance and Reality' and 'The Semantic Conception of Truth'

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4 ideas

5. Theory of Logic / D. Assumptions for Logic / 2. Excluded Middle

19192	The truth definition proves semantic contradiction and excluded middle laws (not the logic laws) [Tarski]
	Full Idea: With our definition of truth we can prove the laws of contradiction and excluded middle. These semantic laws should not be identified with the related logical laws, which belong to the sentential calculus, and do not involve 'true' at all.
	From: Alfred Tarski (The Semantic Conception of Truth [1944], 12)
	A reaction: Very illuminating. I wish modern thinkers could be so clear about this matter. The logic contains 'P or not-P'. The semantics contains 'P is either true or false'. Critics say Tarski has presupposed 'classical' logic.

5. Theory of Logic / F. Referring in Logic / 1. Naming / b. Names as descriptive

10999	Names need a means of reidentifying their referents [Bradley, by Read]
	Full Idea: Unless a name has associated with it a means of reidentifying its referent, we cannot use it.
	From: report of F.H. Bradley (Appearance and Reality [1893]) by Stephen Read - Thinking About Logic Ch.4
	A reaction: Brilliant! This point is totally undeniable. It is not enough that someone be 'baptised'. We need to hang onto both the name and what it refers to, and how are we going to do that?

5. Theory of Logic / K. Features of Logics / 5. Incompleteness

17894	We have no argument to show a statement is absolutely undecidable [Koellner]
	Full Idea: There is at present no solid argument to the effect that a given statement is absolutely undecidable.
	From: Peter Koellner (On the Question of Absolute Undecidability [2006], 5.3)

5. Theory of Logic / L. Paradox / 6. Paradoxes in Language / a. The Liar paradox

19187	The Liar makes us assert a false sentence, so it must be taken seriously [Tarski]
	Full Idea: In my judgement, it would be quite wrong and dangerous from the point of view of scientific progress to depreciate the importance of nhtinomies like the Liar Paradox, and treat them as jokes. The fact is we have been compelled to assert a false sentence.
	From: Alfred Tarski (The Semantic Conception of Truth [1944], 07)
	A reaction: This is the heartfelt cry of the perfectionist, who wants everything under control. It was the dream of the age of Frege to Hilbert, which gradually eroded after Gödel's Incompleteness proof. Short ordinary folk panic about the Liar?