Aristotle taught rules for correctly finding the truth by using deductive reasoning. He established more than a score of patterns that deductive reasoning can follow. He called these patterns syllogisms . A syllogism is a test for deductive reasoning. Just to show you how they work, we will look at two very common kinds of syllogisms, categorical and hypothetical.
All grapefruits are citrus fruits.
Ruby Reds are citrus fruits. All grapefruits are citrus fruits. Therefore, tangelos are grapefruits. Of course, this is quite wrong. Names of mistakes in reasoning are steeped in history and often are very colorful.