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" suggests they are two separate things. If my understanding of 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?

Note: The reason I have posted this on philosophy stack exchange is because logic is very much a philosopher's word and they have a better understanding of its meaning (there is also terminology/definition tags showing that these questions can be asked) You wouldn't use english-usage stackexchange to ask the meaning of a words from science eg "what is the difference between kenetic energy and Newtons?"

  • 1
    As originally written this is a grammar question, not a philosophy question, however, I think the OP may have actually intended a philosophy question. I will edit to highlight this --@RayKay please edit it back if these edits change your intention. Commented Feb 10, 2015 at 14:36
  • I've always felt that we use reason to make rational choices in situations where logic fails. All those real-life choices that come down to personal preference and gut feel.
    – user4894
    Commented Feb 10, 2015 at 23:25
  • @ChrisSunami I have made it more specific.
    – Ray Kay
    Commented Feb 11, 2015 at 3:36
  • Reason and logic are used to make rational decisions. Logic needs to be tempered with reason and vice versa.
    – user46038
    Commented Apr 5, 2020 at 18:48
  • Can you add detail to this brief entry? Commented Apr 5, 2020 at 19:30

4 Answers 4


Remember Kirk and Spock. Spock is the man of logic. But Kirk is the man of reason. Kirk always figures out the right thing to do in any situation; even when Spock raises an eyebrow and says, "But Captain, that's illogical!"

Reason is not the same thing as logic. As is so often the case, Wikipedia supplies valuable context.

Reason is the capacity for consciously making sense of things, applying logic, establishing and verifying facts, and changing or justifying practices, institutions, and beliefs based on new or existing information.

As we see, logic is one set of tools we apply after doing a lot of other homework ... not only establishing facts, but also putting them in the context of our own preferences and desires.

If logic was all that existed, commerce could not exist. A seller holds a good, a buyer holds currency. By "logic," one is greater than the other, and no trade can occur. But each using their own reason, the seller values the money higher than the good; and the buyer holds the reverse values. They trade and they are both happy. If pure logic prevailed, this could not happen. One party would have to lose and the other win. But preferences are subjective; even though logic is objective. Thus reason encompasses more than logic.

One could give many examples. There's a story reported in the newspaper. One person believes the story, another doesn't. They then take rational actions based on their information and beliefs; but they each take different actions.

Two machines given the same programming will produce the same output for a given input. Two humans often do something different given the same inputs.

Reason is much more powerful than logic. If there is insufficient information, or contradictory information, logic is powerless. But reason can always find a sensible course of action.

As I noted in my comment above: We use reason to make rational choices in situations where logic fails.

Isn't that pretty much the common everyday experience of everyone? You go to get your morning coffee. Is coffee bad for you? Maybe. It's a mildly addictive stimulant. Is it good for you? Maybe. Some think it forestalls diabetes. It's full of antioxidants. Are those good for you? I guess so, I saw it on the Internet. But what about the beans? Are they fair traded? Was someone unfairly exploited in the production of those beans? How much do I care? How much can I know, even if I spent all my time and energy trying to find out? And what about the milk? Whole or 2% or none? Are the cows being mistreated or are they happy? Pros and cons to every choice. Sugar or artificial or none?

Does your brain lock up in an infinite spiral of confusion? For some people whose rationality is compromised, that's exactly what happens. For normal people, we are aware of all that information but we put it in its proper perspective: things we can't do anything right now. We have our coffee. Or not, if we prefer not. Either way we're using our rationality to cut through a mass of facts and rumors that can not possibly be analyzed to their last detail.

Where is logic? If a perfectly logical being existed, it could not function. It couldn't even get a cup of coffee in the morning. But you and I function just fine. Our reason allows us to put all that overwhelming and conflicting information in proper context ... which is that in the scheme of things, it's all not very important. Unless the individual chooses to make those things important. Maybe you refuse to drink beans that aren't organic and fair-traded. Maybe I order a cup and don't think about it much.

We're both being rational. Neither of us is being logical. Logic is hopeless in deciding whether and how to have your morning coffee. Only reason can save us. Logic's useless. Reason lets you ignore all the inputs that simply don't matter.

Reason is what lets you function in a world of conflicting information, where logic fails.


So many ways to get after it:

Logic is deductive/Reason is inductive

Logic is formal/Reason is common sense

Logic is systematic/Reason normative

Logic is form/Reason is function.

And depending on your metaphysical leanings, they may be the same!


Logic regards necessary relations among abstractions.

Reason regards whether they are good abstractions.


Logic & reason

Gil Harman has worked at this distinction and his views, usefully summarised below, provide at least some materials for reflection.

Difference 1 - reasoning, logic and belief revision

Reasoning is a procedure for revising one's beliefs, for changing one's view, for modifying one's intentions and plans. This must not be confused with argument for, or proof of, a conclusion, which is a matter of proceeding from premises via a series of intermediate steps. In fact Harman thinks that there is a category difference between reasoning (reasoned change in view) and argument or proof. His point is that a rule of argument is a principle of implication which tells us that propositions of a certain sort imply other propositions of a certain sort, but tells us nothing about belief-revision, so that 'rules of argument are not by themselves rules for revising one's view' (Harman, 1986, p. 3).

The rules of logic are permissive rules licensing the deduction of propositions. By applying such rules, we can generate more and more logical consequences from an initial set. Now, in reasoning, Harman points out, we not only add to our beliefs but sometimes subtract from the beliefs held in store and this, he claims, illustrates one vital difference between logical proof and reasoning. Another difference, he suggests, is that, unlike logical principles, principles of belief revision are defeasible - they don't hold in all instances. Consider, for example the following principle of belief-revision: Tf one believes p and also believes if p then q then one can infer q. Unlike modus ponens, this principle does not always hold. Harman constructs a counter instance:

Mary believes that if she looks in the cupboard, she will see a box of Cheerios. She comes to believe that she is looking in the cupboard and that she does not see a box of Cheerios. At this point, Mary's beliefs are jointly inconsistent and therefore imply any proposition whatsoever. This does not authorize Mary to infer any proposition what? soever. Nor does Mary infer whatever she might wish to infer. Instead she abandons her first belief, concluding that it is false after all. (Harman, 1986, p. 5)

In other words, if a logical consequence of some of the propositions we believe is absurd or otherwise unacceptable, then the thing to do is to revise or relinquish some of our beliefs, rather than to accept that logical consequence.

Difference 2 - logic and the infinity of conclusions

Again, principles of logic permit the drawing of an infinite number of conclusions from a set of premises. The premises p and q imply p & q, (p & p) & q, (p v q) & q & q and so on. But it can hardly be a principle of reasoning that we should accept (i.e., explicitly embrace) a vast number of useless consequences of our beliefs, for that would be to clutter the mind with useless trivialities (Harman, 1986, pp. 5-6, 12-13, 41-42). Harman makes much of this point, and advocates a Principle of Clutter Avoidance which is 'a metaprinciple that con? strains the actual principles of revision. The principles of revision must be such that they discourage a person from cluttering up either long-term memory or short-term processing capacities with trivialities' (Harman, 1986, p. 15). For Harman, to have an explicit belief is to have a representation - some sentence-like entity - in the brain (Harman, 1973, 1977, 1986, pp. 12-14, 32) so clutter-avoidance is a serious matter of preventing the brain bursting.

Difference 3 - logic, reasoning, and logical inconsistency

Finally, Harman objects to the idea that the relevance of logic to reasoning is captured by the suggestion that, in reasoning, one seeks to avoid logical inconsistency. Harman invites us to observe that we sometimes discover that we hold inconsistent beliefs but, unable to find a satisfactory way of revising them, we retain them 'while trying not to exploit the inconsistency'. (Wittgenstein once took exactly this line, but later changed his view.) Harman also points to situations where one believes that not all one's beliefs could be true. He comments that here one might well be justified in continuing to believe that and each of one's other beliefs as well (Harman, 1986, pp. 15-16). Likewise, according to Harman, the proper, rational, response to semantical paradoxes such as the Liar is to retain the Biconditional Truth Schema '"p" is true if and only if p' as a kind of 'default assumption', while recognizing that, when paradoxical sentences are substituted for 'p' in the Schema, contradiction ensues. So the Schema holds 'normally', but not without exception. Harman comments: 'This does not seem to be a satisfactory solution from the point of view of logic, since we take logic to require precise principles with precise boundaries, not principles that hold merely 'normally' or 'other things being equal'. But in ordinary life we accept many principles of this vaguer sort (Harman, 1986, pp. 16-17).

Harman concedes that we do have the disposition to avoid embracing propositions we see to be inconsistent, but it is not just logical inconsistency that we are so disposed to avoid. For example, we don't accept both 'X is y's brother' and 'X is female' nor both 'Today is Thursday' and 'Tomorrow is Saturday' (Harman, 1986, pp. 17-19). So there is no special relevance of logic.

(Laurence Goldstein, 'Logic and Reasoning', Erkenntnis (1975-), Vol. 28, No. 3 (May, 1988), pp. 297-320: 297-9.


Harman, G.: 1973, Thought, Princeton University Press, Princeton, New Jersey.

Harman, G.: 1977, 'How to use Propositions', American Philosophical Quarterly 14, 173-76.

Harman, G.: 1979, '"If" and modus Ponens', Theory and Decision 11, 41-53.

Harman, G.: 1982, 'Logic, Reasoning and Logical Form' in T. W. Simon and R. Scholes (eds.), Language, Mind and Brain, Erlbaum, New York.

Harman, G.: 1984, 'Logic and Reasoning', Synthese 60, 107-27.

Harman, G: 1986, Change in View, MIT Press, Cambridge, Massachusetts. ,

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .