How is this argument begging the question?

P1) 18-year-olds are mature enough to drink.

P2) All people who are mature enough to drink should be allowed to drink.

P3) If you are to be allowed to drink, you must be of drinking age.

P4) 18-year-olds are not of drinking age.

C) The drinking age should be lowered to 18.

The author of the site attempts to explain it, but I can’t follow what he’s saying. I only provided the hyperlink to give him/her credit. But can anyone in plain English tell me why this argument begs the question?

  • 2
    How does P1 differ from the conclusion?
    – virmaior
    Aug 17, 2016 at 2:53
  • 2
    Conclusion C is little more than rephrasing of premise P1, anyone who accepts P1 would likely accept C, and conversely, anyone who rejects C will reject P1. It is P1 that one should argue for to begin with, and the argument given instead is largely a pointless triviality. It "begs the question" by taking for granted the main point to be argued, and the obvious response is to ask it: what makes you assume P1?
    – Conifold
    Aug 17, 2016 at 2:54
  • 1
    just to be clear: the conclusion C is not already included in any of the premises, which is what begging the question means. And contrary to what your citation claims, begging the question has nothing whatsoever to do with objections. That's just preposterous.
    – user20153
    Aug 17, 2016 at 20:38
  • 1
    this begs the question: "18-year-olds should be allowed to drink legally. The drinking age is 21. Therefore the drinking age should be lowered to 18." The conclusion is already there in the premise. It's a fallacy because there is no real reasoning involved.
    – user20153
    Aug 17, 2016 at 20:45
  • 1
    or more humorously: why should the drinking age age be lowered to 18? well, because 18-year-olds should be able to drink legally!
    – user20153
    Aug 17, 2016 at 20:47

4 Answers 4


This is not question-begging.

To claim that argument is question-begging is to conflate the two statements "X is mature enough to drink" and "X should be legally allowed to purchase and consume alcohol". These are not the same statement.

For example, someone might argue that allowing 18 year-olds to shop at liquor stores would be a bad idea due to consequence X, even if they are mature enough to drink. I'm not saying any such argument would be something I'd agree with, only that the argument cannot be ruled out on purely logical grounds.

Essentially what I am saying is that P2 above is an arguable statement, which should be backed up with facts, etc. To claim the overall argument is "begging the question" is in essence claiming P2 is a tautology, which it is not.

  • I would add that the question involves modals. "Should be allowed " and "is allowed" are very different.
    – user20153
    Aug 17, 2016 at 20:22
  • and in fact it's a perfectly reasonable argument, which can be restated more perspicuously: the drinking age is 21. 18 years should be allowed to drink. therefore the drinking age should be lowered to 18.
    – user20153
    Aug 17, 2016 at 20:27
  • The consequence X would have to affect 18-21 year olds, but not older, and for reasons unrelated to their immaturity. That is so implausible on its face as to be disregarded in practical terms, barring strong evidence to the contrary. I am afraid that if we become too legalistic and formalistic about it no argument about real matters can be allowed at all, because every sentence would have to be conditioned on an infinity of ceteris paribus clauses about remote possibilities. Informal arguments do not conform to mathematical standards by design.
    – Conifold
    Aug 17, 2016 at 23:10

In plain English: "Begging a question" involves someone attempting to prove or deduce a proposition based on a premise that itself requires proof or a convincing justification. The argument given is begging the question because P1 requires proof or a convincing justification, but none is provided.

NOTE: Without either a proof or a convincing justification, a premise is no more than an unwarranted assumption, which could contain, either directly or indirectly, the conclusion. P1 is an unwarranted assumption. If we take the other premises to be warranted, then P1 must contain, indirectly, the conclusion, which is then itself unwarranted. That would mean the argument begs the question. That said, there are other problems with the argument. For example, P2 and P3 are inconsistent in that people who under age 18 but who are mature enough to drink would be prohibited from doing so by the establishment of a drinking age of 18 years of age.

  • No, question-begging means using your conclusion as one of your premises. It has nothing to do with whether a premise "requires proof". You either find a premise convincing or you do not; further arguments can be made for or against specific premises, but those are separate arguments. Premises are not meant to be already-proven facts, they are premises upon which the argument is based.
    – Era
    Aug 19, 2016 at 21:22
  • @Era Agree. Broadened "proof" to "proof or convincing justification" and added NOTE. Aug 19, 2016 at 23:59

Notice the complete reasoning in the link you give:

(12) A: "The drinking age should be lowered to 18, because 18-year-olds are mature enough to drink."

Context: B's reason for disputing the conclusion is the same as [the] reason for disputing the premise here.

So, the problem is, B already agrees that people who are mature enough to drink should be able to drink legally; what she disagrees is that 18-year-olds are mature enough to drink. Unless she can be convinced of the latter, this begs the question, "but why do you think 18-year-olds are mature enough to drink"?

(So, another argument, like for instance, "driving age is 18; don't you think that driving requires more maturity than drinking?" is necessary to sway B.)

Notice that the "context" could be different:

Alternate Context: B's reason for disputing the conclusion is different from her reason for disputing the premise here.

Here B agrees that 18-year-olds are mature enough to drink, but she has a different reason for opposing the lowering of drinking age (perhaps she thinks alcohol should be forbidden for all ages, and sees a 21 year age of drinking as a lesser evil than a 18 year age of drinking (and yes, this is a reasonable position; check your own opinion about heroin, for instance)). In this case, the argument would not be begging the question (or that precise question, anyway).

  • As @mobileink noted in comments on the OP, the reason for an objector's rejection of an argument/premise (the context) is irrelevant to whether an argument is in itself question-begging.
    – Jeff Y
    Aug 18, 2016 at 19:15

But can anyone in plain English tell me why this argument begs the question?

The logical fallacy of, "Begging the Question" is simply using circular reasoning; more specifically the justification of the claim assumes the conclusion.

The author of the original piece states there is something wrong about this argument, however points out premise 1 may be flawed for other reasons.

An easier to understand example of begging the question would be, When did you stop hitting your wife? Which implies you beat your wife before some time in the past.

The example provided are poor examples of begging the question since they are clear examples of circular reasoning. It appears you are looking for more simplified examples and explanations; this resource is along those lines: https://yourlogicalfallacyis.com/begging-the-question

  • This is a general explanation about begging the question, but doesn't answer the question about this specific example.
    – user2953
    Aug 18, 2016 at 7:29
  • hmm? I stated the specific examples are terrible and implied they should be disregarded. I then provided a clear example and a good resource the OP asked for.
    – Dave
    Aug 18, 2016 at 8:07

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