LPL 4.2 lecture

# LPL 4.2 lecture - Logical and tautological equivalence In...

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Logical and tautological equivalence In the last chapter we discussed the notion of logical equivalence. We say that two sentences are logically equivalent when they have the same truth values in every possible circumstance. In this chapter, we want to discuss tautological equivalence , which is a certain type of logical equivalence. Two sentences are tautologically equivalent if they can be understood to be equivalent to one another simply in virtue of the truth-functional connectives they contain. We can check for tautological equivalence using truth tables. Suppose we want to know if two sentences are tautologically equivalent. We need to construct a truth table with reference columns for each atomic sentence that appears in our two sentences. Then, to the right of the reference columns, we need to place the two sentences in question. Once the truth table is complete, we check for tautological equivalence by looking to the columns under the main connectives in each of the two sentences. If these

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## This note was uploaded on 02/10/2011 for the course PHIL 110 taught by Professor ? during the Spring '06 term at South Carolina.

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LPL 4.2 lecture - Logical and tautological equivalence In...

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