I really believe that one cannot derive " ought" from "is".

But the case of linguistic usage causes me some intellectual trouble.

(1) Linguistic usage is a simple fact.

(2) Linguistic usage often deviates from linguistic norm, from correct speech ( from a phonetic, semantic, syntactic aspect...)

(3) Incorrect linguistic usage often becomes correct, by the simple fact that it is the most common usage, and/or the fact that it is deep-rooted.

(4) So, assuming one wants to speak correctly, one ought to conform to linguistic usage. In language, the fact of usage has a genuine normative value.

Hence the question : is the case of linguistic usage a genuine couterexample to the rule " ought cannot be derived from is"?


If usage were not normative, the following extract from Through the looking glass would not be so funny I think :

"I don't know what you mean by 'glory,' " Alice said.

Humpty Dumpty smiled contemptuously. "Of course you don't—till I tell you. I meant 'there's a nice knock-down argument for you!' "

"But 'glory' doesn't mean 'a nice knock-down argument'," Alice objected.

"When I use a word," Humpty Dumpty said, in rather a scornful tone, "it means

just what I choose it to mean—neither more nor less."

"The question is," said Alice, "whether you can make words mean so many different things."

"The question is," said Humpty Dumpty, "which is to be master—that's all."

Alice was too much puzzled to say anything, so after a minute Humpty Dumpty began again. "They've a temper, some of them—particularly verbs, they're the proudest—adjectives you can do anything with, but not verbs—however, I can manage the whole lot! Impenetrability! That's what I say

  • ...and what if one does not want to speak correctly?
    – H Walters
    May 25, 2019 at 21:44
  • @HWalter. In the same way as Humpty Dumpty in Through the looking glass? ( I've added a quote in the post).
    – user37859
    May 25, 2019 at 22:36
  • @HWalters. I've expressed the necessity as a hypothetical imperative. But in fact, speaking correctly is not optional. Analogously, one could say that " if one wants to speak honestly, one should not lie". But that does not mean that " speaking honestly" is an option. No one could say " yes, I've lied, that's because I don't mind speaking honestly". The alledged reason given by the liar would not count as valid. In the same way one could not say for example " the bestaurant" ( instead of ' the restaurant" ) arguing one does not want to speak correctly.
    – user37859
    May 25, 2019 at 22:51
  • Speaking correctly is absolutely optional, writing correctly too. even speling corectly. Speaking correctly isn't even necessary nor sufficient for being understood; some people speak incorrectly but are easy to understand, others correctly but it's all nonsense. If I accept that I ought to speak correctly, since by definition that conforms to a norm, then I ipso facto accept that I ought to conform to that norm. I also must wear a seatbelt if I want to drive legally, because that's the law and by definition driving legally means following the law. What was your question?
    – H Walters
    May 26, 2019 at 0:18
  • One cannot derive an "ought" from an "is" alone. However, "linguistic usage" is full of enthymemes, arguments with implicitly assumed premises omitted for expediency, including general oughts. For example: "nicotine is harmful for your health ("is"), so you should quit smoking ("ought")". That one ought not harm their own health unnecessarily is a natural ought for humans to share, and there is little point to repeating it each time. So there is nothing wrong with liguistic usage even when it does "derive" an ought from an is.
    – Conifold
    May 26, 2019 at 8:59

1 Answer 1


You gave an example of a hypothetical imperative.

It's an if-then statement and there's nothing wrong with it. But you derived your ought from an if, not an is.

You cannot directly derive an ought from an is. Indirectly, yes, you can use "if" statements to do the job.

The problem with this is that you have to assume something which isn't necessarily the case, so it can't be put as a categorical imperative.

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