Logic

If you read the first chapter in a book on ‘Introduction to Logic’ or attend the first class in the first year of a logic course, you learn about these notions. Almost one of the first things you learn is this: there is a fundamental asymmetry in the transmission of truth and falsity from premises to conclusions. Truth is transmitted from premises to conclusions but falsity is not; falsity is transmitted from the conclusion to premises but truth is not. (In both cases, we assume that valid rules of logical inferences are used.) That is to say, if your premises are true and you use valid rules of inference, then your conclusion is also true; if your conclusion is false and you use valid rules of inference then at least one of your premises is false. However, the other way does not hold: you could have false premises and yet draw true conclusions. The falsity of your premise does not make your conclusion false or the truth of your conclusion does not make all your premises (or even one of them) true. This is the nature of drawing conclusions in deductive logics. Because this is the first thing you learn in your logic course, I have also formulated in a simple language.

-- S.N. Balagangadhara

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