Logic formalizes valid methods of reasoning. The study of logic was begun by the ancient Greeks whose educational system stressed competence in reasoning and in the use of language. Along with rhetoric and grammar, logic formed part of the trivium, the first subjects taught to young people. Rules of logic were classified and named. The most widely known set of rules are the syllogisms; here is an example of one form of syllogism:
If both premises are true, the rules ensure that the conclusion is true.
Premise All rabbits have fur.
Premise Some pets are rabbits.
Conclusion Some pets have fur.
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