Chapter 6

Contra-positive Claims

The importance and requirements of a contra-positive claim is taught in Chapter 6 of Epstein. Two claims have to be true in order for them to be equivalent to each other. Contra-positive statements are defined as the situation in which a claim and a contra-positive claim are related or similar. Both claims must coincide; either true or both false. 

The following are examples of true claims; a contra-positive statement:

a. Hard working students get good grades.

b. Students that complete all their homework and class work assignments will get good grades.

The following are examples of contra-positive statements including a sufficient condition; which the first claim is sufficient for the second claim. (There are 4 different types of conditions:

Direct, indirect, affirming the consequent, and denying the antecedent)

a.     Eileen always dips eats pizza with ranch.  If Eileen is eating pizza, she is eating ranch.

Reasoning with “OR” claims

No matter how many or’s are in the argument, only one may be the right conclusion. A reader must narrow down all the possibilities to get the correct conclusion. By determining which ones are most valid, it makes it easier to find the conclusion.

The couple decided they were either going to go out on a date or stay in depending on the weather, but because storm clouds were coming in, they decided to stay in and avoid the rain.

By reasoning with “OR”, the argument is valid because there is no way the premise to be true and the conclusion false. The premise was the first sentence about where the party should occur. The conclusion stated that the party would be celebrated in their backyard.