Notes 6.4
Truth Tables for Arguments
In order to test for validity in an argument using truth tables, all we have to do is the
following:
1.
Symbolize the argument (if necessary—it won’t always be on the test) to
represent the simple propositions.
2.
Write out the symbolized argument, placing a single slash between the premises
and a double slash between the last premise and the conclusion.
3.
Make a truth table for that argument as if it were a normal proposition broken into
parts.
4.
Look for a line in which all of the premises are true and the conclusion is false.
If
such a line obtains, then the argument is invalid; if not, then it’s valid.
This ought to make sense according to how we’ve defined validity all semester long.
For
deductive arguments, we’ve defined invalidity by possibly having true premises and a
false conclusion (i.e., if we assume true premises, we better not have a false conclusion—
or else the argument is invalid.).
This truth table method gives us all the possibilities of
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 Spring '08
 Barrett
 Logic, Conclusion, Logical connective

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