In a blog-post I wrote:

What makes the puzzle singular is that countless professional mathematicians refused to believe what they read when the following week Marilyn vos Savant duly gave the correct answer along with how one should reason about it.

I meant to say “... she showed how one should come to the correct solution following the given logical steps.”

An English teacher remarked that she had never heard of the phrase to reason about.

1) Is the quoted usage correct in the above sense?

2) Irrespective of my usage, is it correct to use “to reason about” when it makes sense?

  • Quick google search suggests it exists google.de/…
    – Emanuel
    Apr 14, 2015 at 12:42
  • @Emanuel, I am aware that it exists, but I am yet to find an official definition.
    – blackened
    Apr 14, 2015 at 12:43
  • Why does it need to be a set phrase or an idiom? to reason as a verb (defn 2 here) is perfectly fine with about something
    – blgt
    Apr 14, 2015 at 13:01
  • What is the puzzle? Apr 14, 2015 at 16:05
  • @dennisdeems Monty Hall
    – blackened
    Apr 14, 2015 at 16:08

4 Answers 4


The phrase "reason about" does in fact have a precedent for being used, and in the snippet you've posted, it is used correctly. Not surprisingly, the question of whether a person has heard this before is wholly dependent on the forms of writing and speech to which that person has been exposed. Your teacher—of what nationality is she? The phrase "reason about" is far more common in Great Britain than it is anywhere else in the world, and I'd not be wholly surprised to hear some American know-it-all claim it to be wrong.

However, being that your English teacher is an English teacher, she should be well ashamed. She should understand perfectly well that the fact that she's never heard a thing before certainly is not adequate proof for concluding that the thing in question is wrong, and anyway, one such precedent for use of this phrase is very well known amongst English readers and teachers. As soon as I saw this question, a snippet of Lewis Carroll's long poem "The Hunting of the Snark" came immediately to mind. You will find the following bit in the section "Fit the Fifth: The Beaver's Lesson":

"Taking Three as the subject to reason about—
    A convenient number to state—
We add Seven, and Ten, and then multiply out
    By One Thousand diminished by Eight.

"The result we proceed to divide, as you see,
    By Nine Hundred and Ninety and Two:
Then subtract Seventeen, and the answer must be
    Exactly and perfectly true.

  • 2
    One problem with citing Lewis Carroll is that he would of course deliberately write some strange things, so that he is writing normally here is not necessarily obvious (though he certainly is). Luckily we can add "She could not reason about them as about people whose feelings went by the same rule as her own did." from Woolf's The Voyage Out, "A man, who has to reason about his duty,..." from William Paley and plenty more.
    – Jon Hanna
    Apr 14, 2015 at 14:24
  • 1
    "The Hunting of the Snark" is hardly full of nonsense language. In fact, it is full of perfectly intelligible nonsense. But there's the trick, isn't there? Carroll was an intelligent writer, and in the case of "The Hunting of the Snark", he was very careful to use real words in ways that people could easily understand. Of course, Woolf and Paley offer other citations, and a quick Google search can turn up a happy dozen or more in fewer than five minutes--and many of those come from contemporary sources, even.
    – R Mac
    Apr 14, 2015 at 14:35

The pairing is not only good plain English understandable solely by considering reason and about, but given explicitly in the OED:

  1. intr. To think in a connected or logical manner; to employ the faculty of reason in forming conclusions.

a. With from (a premise or datum); about, †of, upon (a subject).


This does not seem to be correct to me in BrE.

I would, however, expect to see "...with how one should reason it out"

reason something out

to figure something out; to plan a reasonable course of action. Now let's be calm and try to reason this out. Let us reason out our difficulties.


  • BrE is not very precisely defined of course, but to my British ears "reason it out" more like AmE than BrE. Personally I would say "think it out" not "reason it out".
    – alephzero
    Apr 14, 2015 at 18:11
  • Actually I would almost certainly use "work it out" myself, rather than "reason it out", but I don't think the latter is particularly rare round these parts. I think the use of "reason" in 'reason it out' tends to imply that logic should be used to construct the outcome, whereas 'work it out' means more like 'compute the answer'... clearly there are locality shades and flavours as would be expected...
    – Marv Mills
    Apr 14, 2015 at 19:18

The thing is, when you use a preposition after a verb, people tend to parse it as a phrasal verb and look for the idiomatic meaning.

In this case, none exists. That's why it doesn't "sound right".

As blgt pointed out in their comment, the use of reason as a pure verb here is grammatically correct.

But still, to avoid the ambiguity, you should rephrase it. One way to do that is reason it out, like Marv said. EDIT: Reason it out may imply more people than you mean

  • 2
    Except that it is indeed in being used in its idiomatic meaning, and that's why it sounds correct. Replacing it to "reason it out" would be very wrong, as that does not mean the same thing.
    – Jon Hanna
    Apr 14, 2015 at 14:27
  • @JonHanna: I think what you meant is it's NOT idiomatic and used as plain words. But your second point is valid. I don't think the downvote was called for.
    – Tushar Raj
    Apr 14, 2015 at 14:36
  • 1
    No, I mean that while it can be understood as the sum of its parts, it's also a well-used enough pairing to count as a idiom. I think a downvote is fair when you suggest someone re-write one thing to be another completely different thing.
    – Jon Hanna
    Apr 14, 2015 at 14:43
  • @JonHanna: Idiom, by definition, is NOT the sum of its parts oxforddictionaries.com/definition/english/idiom
    – Tushar Raj
    Apr 14, 2015 at 14:46
  • 2
    But idiomatic is, ironically enough, not the sum of its parts of idiom and atic: oxforddictionaries.com/definition/english/idiomatic "Using, containing, or denoting expressions that are natural to a native speaker"
    – Jon Hanna
    Apr 14, 2015 at 15:00

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.