From the course: Programming Foundations: Discrete Mathematics

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Rules of inference

Rules of inference

From the course: Programming Foundations: Discrete Mathematics

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Rules of inference

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- [Voiceover] When evaluating arguments for validity, there are several rules of inference that can make the process much easier. The idea is to take the original argument and label each predicate with a unique variable. Then rewrite the problem using the variables, the logical connectors, and conditional statements such as and, or, if then, not, et cetera. Here's an example. In this argument it says if it rains, Cy will be sick. Cy is not sick, therefore it did not rain. Okay, let's label each predicate. If it rains can be P. Cy will be sick is going to be Q. Cy is not sick will be not Q. Therefore, it did not rain, not P. Now I can say P then Q for the first sentence. That means if it rains, Cy will be sick. The next premises or hypothesis is not Q, meaning that Cy is not sick. Therefore, not P. Now we can look at the rules of inference to find a match to our format. If we find a match, we know this is a valid argument. Let's review the rules of inference. The first one is modus…

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