I have always interpreted logic to mean a systematic form (premise-reason-conclusion) of reason. So it seems that you are saying one word (reason) and a branch of that word (logic). But the "and" suggest they are two separate things. If my understanding if these two word are correct, it would be like saying "science and biology". As biology is a branch of science. Is logic considered a branch word of reason? Or are these two separate words?

  • 1
    two nouns joined by and certainly fit in a lot of grammatically correct sentences. Perhaps you are asking whether their pairing is semantically acceptable? But to answer that you'd need to provide a sentence with some context, and at that point we'd probably say that the question is off-topic because it's about Logic and Reason and not about the English language.
    – Jim
    Feb 11, 2015 at 3:45

2 Answers 2


Reason does not need to be logical (one can argue that reasoning is):

The basis or motive for an action, decision, or conviction; a declaration made to explain or justify action, decision, or conviction; a fact or cause that explains why something exists or has occurred; a premise, usually the minor premise, of an argument. (TFD)

Reason is basically answering the question why. It implies rationality.

Logic is a systematic approach to a problem.

The study of the principles of reasoning, especially of the structure of propositions as distinguished from their content and of method and validity in deductive reasoning; a system of reasoning: Aristotle's logic; a mode of reasoning; the formal, guiding principles of a discipline, school, or science. (TFD)

To me, logic is the way one arrives at an answer.

Pre-Socratic philosophers did not appear to follow any logical principles; reason was descriptive rather than prescriptive, a way to understand how people actually think rather than how they ought to think.

This may be a 'semantic unit' handed down to us by philosophers. However, I don't think it's necessarily tautological, as you seem to imply.

  • In the definition you offer for 'reason', you seem to be covering one of the word's meanings; in that meaning, it is a countable entity, and therefore, it should be preceded by an article (He offered a reason for his decision.) I'm under the impression that the OP is considering another meaning of 'reason': a certain capacity of the human mind.
    – anemone
    Feb 11, 2015 at 8:10

It is not only grammatically correct, it is semantically meaningful.

It is very common to see "defies all logic and reason" used in various arguments (perhaps a bit dramatically). A Google search on that phrase gives well over 100,000 hits. The simple search "logic and reason" yields over 400,000 hits.

Admittedly Google hits are not definitive, but they do give a good indication of the relative usage of a phrase.

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