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This document discusses logical arguments and validity. It defines key logical terms like conclusions, premises, valid arguments, and different types of valid and invalid reasoning forms. Examples are provided to illustrate necessary and sufficient conditions.
In this section you will learn what causes inductive and deductive arguments to be good or bad and the language used to classify them as such. This section introduces the central ideas and terminology needed to evaluate arguments— to distinguish good arguments from bad arguments.
Why Focus on Validity? Valid arguments are maximally reliable, in the sense that if the premisses of a valid argument are true, then the conclusion must be true. For various reasons, philosophers have an interest in conclusive arguments (at least, apparently conclusive arguments). We are going to begin to provide a systematic account of good ...
Examples of valid argument forms Fallacies and contradiction rule Valid and invalid arguments De nition An argument form is called valid if no matter what particular statements are substituted for the statement variables in its premises, if the resulting premises are all true, then the conclusion is also true.
To test whether or not an argument is valid, we do the following: Look for all the rows where the premises are all true - we call such rows critical rows. If the conclusion is false in a critical row, then the argument is invalid. Otherwise, the argument is valid (since the conclusion is always true when the premises are true).
determine the validity of abstract argument forms, we have to hone our skills in logical parsing, when we want to use logical theory to evaluate concrete pieces of discourse to see whether they in fact express valid arguments.
Building Valid Arguments • A valid argument is a sequence of statements where each statement is either a premise or follows from previous statements (called premises) by rules of inference. The last statement is called conclusion. • A valid argument takes the following form: Premise 1 Premise 2 Conclusion Premise n ∴
