I'm having trouble understanding how something can be rational, logical, or both.

I had understood up to this point that they could be used interchangeably, but now I've been told that that's not quite true.

Does it not depend on context and circumstances?

Are there examples where something can be logical at one point and later become rational but not logical?

These concepts confuse my greatly.

I would have posted this on a psychology-themed site, but StackExchange doesn't have one from what I can tell. I will delete this post if it is deemed inappropriate for this site.

I've never taken a course on any of the related topics.

I'm simply trying to understand how something can be logical as well as if that something can also be rational, and if it can later be changed to not be one of the two or neither.

Let's take, for instance, I'm out in the woods and I see a bear.

Would it be logical to run away? If so, is it then also rational to do so?

Why would it be one but not the other or neither?

This is assuming I want to live.

If your response could be presented in a fashion where the common layman could understand, that'd be really helpful. I'm not a philosophy major and I've never taken anything related to the field. Using specialized terms makes the concept more confusing to understand for the general masses.

  • Obviously in many contexts these terms will be used interchangeably. What is the context where someone told you they couldn't be used in this way? Did they give any examples? In academic philosophy, "logic" usually refers to the academic field of formal logic, and "rationality" often refers to a cognitive capacity that may or may not be formal.
    – Dan Hicks
    Commented Sep 26, 2017 at 16:45
  • 1
    "Logic" had a long history with use varying from narrowly formal logic to general theory of arguments, theory of reasoning and even all cognitive philosophy (now called epistemology), see What are the differences between philosophies presupposing one Logic versus many logics? Depending on how narrowly or broadly "logical" is taken it can mean less, more or the same as rational. In ancient Greece logos was a broader concept than ratio, today it is usually the reverse.
    – Conifold
    Commented Sep 26, 2017 at 20:01
  • A) the earth is finite and flat, B) therefore, you can go to the edge of the Earth. The statement "A implies B" is logical (w/ some additional caveats). However, you could argue statement A is irrational. I would say you can have irrational beliefs (axioms in a mathematical sense), and then use perfectly good logic to come up with more irrational beliefs (theorems).
    – user935
    Commented Sep 27, 2017 at 15:59
  • I made an edit to my post. If you all could take a look... Commented Sep 27, 2017 at 16:08
  • @Conifold while your comment is good in general, "ratio" is a Latin word, not Greek. IIRC "logos" was often translated as "ratio" (e.g., in Medieval translations of Aristotle). So your last sentence doesn't seem to make sense.
    – Dan Hicks
    Commented Sep 28, 2017 at 4:27

2 Answers 2


This is an issue that arises often when discussing formal fallacies: Observations are often rational, but not logical. An argument may well be trustworthy but not valid: It may be true, and proven well enough for all practical purposes without being completely well-founded.

One way of looking at it is that logic (the handling of words or meaning, in origin) is about form, and reason (the handling of considerations or concerns, in origin) is about content.

You may not have done the statistics that turn the known facts into well-founded premises, and it may not be possible to do them given what you have at hand. But you can still be pretty sure about your sense of the matter, and that may be reasonable.

So you may not be able to state in simple premises the exact basis upon which you trust your observations, or state the degree of your certainty. But to act on the basis of that certainty is still often rational.

Fallacies arising from slippery slope arguments, cui bono attributions, or maintaining generalizations in the face of a counterexample are logical problems. But they often express a completely rational position.

  • "An argument may well be sound but not valid" > Not in formal logic, where soundness is defined as validity with all true premises.
    – Dan Hicks
    Commented Sep 28, 2017 at 4:22
  • @DanHicks Changed the word.
    – user9166
    Commented Sep 28, 2017 at 17:59

If there is a need to split them, I would look at logical as a data-only type of analysis, without context. If you have a complete set of information that can be reduced to Boolean results, it is possible to get a "purely logical" answer if all are true or all are false.

With the bear, you can define a logical structure that consists of Boolean "run" possibilities. If all of them are known and true, there is only a logical decision - run. Otherwise (e.g., unknown information), even though the "pure logic" is inconclusive, if there are more true than false, the rational thing to do is run.

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