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Ideas for 'On the Question of Absolute Undecidability', 'Notebooks' and 'Truth'

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3 ideas

3. Truth / A. Truth Problems / 1. Truth
Truth consists of having the same idea about something that God has [Joubert]
     Full Idea: Truth consists of having the same idea about something that God has.
     From: Joseph Joubert (Notebooks [1800], 1800)
     A reaction: Presumably sceptics about the existence of objective truth must also be sceptical about the possibility of such a God. I think Joubert is close to the nature of truth here. It is a remote and barely imaginable ideal.
3. Truth / F. Semantic Truth / 1. Tarski's Truth / a. Tarski's truth definition
Truth rests on Elimination ('A' is true → A) and Introduction (A → 'A' is true) [Gupta]
     Full Idea: The basic principles governing truth are Truth Elimination (sentence A follows from ''A' is true') and the converse Truth Introduction (''A' is true' follows from A), which combine into Tarski's T-schema - 'A' is true if and only if A.
     From: Anil Gupta (Truth [2001], 5.1)
     A reaction: Introduction and Elimination rules are the basic components of natural deduction systems, so 'true' now works in the same way as 'and', 'or' etc. This is the logician's route into truth.
3. Truth / F. Semantic Truth / 2. Semantic Truth
A weakened classical language can contain its own truth predicate [Gupta]
     Full Idea: If a classical language is expressively weakened - for example, by dispensing with negation - then it can contain its own truth predicate.
     From: Anil Gupta (Truth [2001], 5.2)
     A reaction: Thus the Tarskian requirement to move to a metalanguage for truth is only a requirement of a reasonably strong language. Gupta uses this to criticise theories that dispense with the metalanguage.