What Is Logic?

Read these out loud: 'The sky is blue.' 'Close the door.' 'Is it raining?' 'Pizza is the best food.' One of these you can mark true or false without arguing. The others you can't. Logic — the engine behind every search bar, password check, and computer chip — is built entirely on that first kind of sentence. Before we can reason, we need to know what we're allowed to reason about.