LPL_3.1_3.3_lecture

# LPL_3.1_3.3_lecture - Negation Conjunction Disjunction In...

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Negation, Conjunction, Disjunction In FOL, atomic sentences have a limited expressive power. Consider the following set of statements: Claire is not taller than Max. Max is at home and Claire fed Scruffy. Either Claire is a student or Max is a student. In order to form more complex statements in FOL, such as those above, we need to combine atomic sentences with connectives . The first set of connectives we will consider are called Boolean connectives and they correspond to the English expressions it is not the case that , and , and or . The Boolean connectives, along with several other we will discuss later, are called “truth- functional” connectives. The reason for this is that the truth value of a complex sentence using Boolean connectives is determined by the truth values of the simple sentences involved. Perhaps the best way to illustrate is to construct a truth table for each connective, showing that the overall truth value of Boolean statements depends on the atomic sentences of which the Boolean statement is composed. For each new connective we introduce into our system, its truth-functional definition will be given by way of a truth table. Negation: ¬ Our first connective ¬ will be used to express negation. In English we might use the expressions not , is not the case that , non- , or un- to express such negation. In FOL, all of these English-language ways of expressing negation can be handled by the ¬ symbol. Suppose that we want to express our first example from above in FOL.

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

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LPL_3.1_3.3_lecture - Negation Conjunction Disjunction In...

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