Abstract

Deductive logic is about the property of arguments called validity. An argument has this property when its conclusion follows deductively from its premises. Here’s an example: If Alice is guilty then Bob is guilty, and Alice is guilty. Therefore, Bob is guilty. The important point is that the validity of this argument has nothing to do with the content of the argument. Any argument of the following form (called modus ponens) is valid: If P then Q, and P, therefore Q. Any claims substituted for P and Q lead to an argument that is valid. Probability theory is also content-free. This is why deductive logic and probability theory have traditionally been the main tools in philosophy of science.