Difference between revisions of "A Prioris"

To negate, an a priori might go, "States is defined as 'a form that matter can take, including solid, liquid, or gas'. It is impossible for a solid, liquid, or gas to eliminate a nuclear arsenal, so the resolution must be false. Therefore, negate." This a priori is, similarly, not smart. However, if conceded, it could be very damaging.  

=== Logical a Prioris ===

Logical a prioris attempt to use the rules of formal logic to prove that the resolution must be true. The most common logical a priori is known as the conditional logic a priori ("condo logic"). Before getting into the argument itself, it is helpful to explain some relevant terminology.

{| class="wikitable"

In the above truth table, the '''Valid''' column is meant to indicate whether the particular combination of <math>p</math> and <math>q</math> being true or false is consistent with the original conditional statement, <math>p \rightarrow q</math>. You can think about it logically. Suppose your friend tells you, "If it is raining, I will bring an umbrella." In row (1), if it is raining, and they bring an umbrella, your friend is holding true to their word. In row (2), it is not raining, yet they still chose to bring an umbrella. This might seem strange at first, but notice that your friend is not contradicting themself. They simply told you that if it would rain, then they would bring an umbrella. They told you nothing about what they would do when it is not raining. Row (4) is also fine; since it is not raining, they do not need to bring an umbrella. Row (3) presents the problem. Your friend promised that if it would rain, they would bring an umbrella. But they didn't!  

Finally, we have enough background to explain the conditional logic a priori. The argument says that the resolution should be viewed as a tacit conditional, or an <math>p \rightarrow q</math> statement. The conditional is, "If the affirmative debater wins the round, then they should get the ballot." The argument (incorrectly) says that denying the antecedent, <math>p</math> , of the statement proves that consequent, <math>q</math> , true. Therefore, if <math>p</math> is false, <math>q</math> must be true. In this context, that means that if the affirmative debater loses the round, they should still get the ballot! The implication, therefore, is that the affirmative debater must get the ballot whether they won or lost the round.  

If you are confused how the argument reached that conclusion, good. The argument is completely invalid! If the antecedent <math>p</math> is false, the consequent <math>q</math> could be either true or false! Look to rows (2) and (4) of the above truth table. Both of these rows are valid (i.e. consistent with the conditional statement), and in row (2), the antecedent is false where the consequent is true, and in row (4), the antecedent is false where the consequent is false. Therefore, the truth or falsity of the antecedent has no bearing on the truth or falsity on the consequent.