Logic 5 - What is a Reductio and Indirect Proof?

In this brief logic lecture, I explain the inference forms called Reductio (ad absurdum) and Indirect Proof. In outline, I do the following five things. First, I review difference between valid inferences and invalid inferences. Second, I entertain a Thought-Experiment to underscore the power of reductio and indirect proof argument forms. Third, I discuss and diagram the Reductio argument form. Fourth, I discuss and diagram the Indirect Proof form argument form, noting the difference between reductio and Indirect Proof. Finally, I talk through an example.