The Nature of Consciousness

Piero Scaruffi

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These are excerpts and elaborations from my book "The Nature of Consciousness"

Truth-conditional Semantics

The US philosopher Donald Davidson was the main proponent of "truth-conditional semantics", which reduces a theory of meaning to a theory of truth.  Tarski simply replaced the universal and intuitive notion of "truth" with an infinite series of rules which define truth in a language relative to truth in another language.  Davidson would rather assume that the concept of "truth" need not be defined, that it is known to everybody. Then he can use the correspondence theory of truth to define meaning: the meaning of a sentence is defined as what it would be if the sentence were true.  The task for a theory of meaning then becomes to generate all meta-sentences (or "T-sentences") for all sentences in the language through a recursive procedure.

This account of meaning relies exclusively on truth conditions.  A sentence is meaningful in virtue of being true under certain conditions and not others.  To know the meaning of a sentence is to know the conditions under which the sentence would be true.

A theory of a language must be able to assign a meaning to every possible sentence of the language. Just like Chomsky had to include a recursive procedure in order to explain the speaker's unlimited ability to “recognize” sentences of the language, so Davidson has to include a recursive procedure in order to explain the speaker's unlimited ability to “understand” sentences of the language. 

Natural languages exhibit an additional difficulty over formal languages: natural languages contain “deictic” elements (demonstratives, personal pronouns, tenses) which cause the truth value to fluctuate in time and depend on the speaker. Davidson therefore proposed to employ a pair of arguments for his truth predicate, one specifying the speaker and one specifying the point in time.

In other words, Davidson assigns meanings to sentences of a natural language by associating the sentences with truth-theoretically interpreted formulas of a logical system (their "logical form").

The US philosopher William Lycan basically refined Davidson's meta-theory. Lycan’s theory of linguistic meaning rests on truth conditions too. All other aspects of semantics (verification conditions, use in language games, illocutionary force, etc.) are derived from that notion. A sentence is meaningful by virtue of being true under certain conditions and not others. However, instead of assigning only a pair of arguments to the truth predicate, Lycan defines truth as a pentadic relationship with the logical form, the context (truth is relative to a context of time and speaker, as specified by some assignment functions), the degree (languages are inherently vague, and sentences normally contain fuzzy terms and hedges) and the idiolect (the truth of a sentence is relative to the language of which it is a grammatical string).


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