Good Math

Show Me Something New!

Now we’ve seen the language of logic: how to read and write statements and how to understand what they mean. But all that we have so far is the language for writing statements. What makes it into a logic is the ability to prove things. Proof in logic is done by inference: inference gives you a way of taking what you know and using it to prove new facts, adding to what you know.

I’m not going to go through the entire set of inference rules allowed in FOPL in detail in this section. I’m just going to give you a couple of examples that are enough to demonstrate a bit of inference. In the next chapter, I’ll show you all of the rules in a more detailed form that’s useful for checking proofs. But for now, here’s a few to get ...