E.g. 1 "Not learning French is my biggest regret."

E.g. 2 "Not to learn French is my biggest regret."

I know that e.g. 1 is correct and e.g. 2 is wrong, but what is the grammar rule making e.g. 2 incorrect?

(At first I thought the rule was that you shouldn't use to-infinitive as the subject, but then I realized it couldn't be the rule as to-infinitive is sometimes used as the subject, as in "To tell the truth is always right.")

  • 1
    I would say 'Not having done something is my regret', and use 'Not to do it' when speaking of future intentions. Jun 22, 2020 at 11:53

2 Answers 2



  • Not learning French is my biggest regret.

but not

  • *Not to learn French is my biggest regret.

Really, the negative is just a distraction. You can't say

  • *To learn French is my biggest regret


The reason is simply that the complex predicate adjective be one's biggest regret does not allow an infinitive subject complement. If if did, it might be extraposed, but, no:

  • *It is my biggest regret (not) to learn French
  • Does the perfect make some of these more acceptable? Maybe it’s just semantic satiety (well, syntactic satiety) but even though I find My biggest regret was to have never learned French unremarkable, I find most similar formulations with not to be clumsy or ambiguous or just plain off: My biggest regret was (not to have / to not have / to have not) learned French. By ambiguous, I mean preliminary uncertainty about whether it’s about to turn into something like My biggest regret was not to have started but to have stopped, which seems to parse ok to me.
    – tchrist
    Jan 16, 2021 at 18:58

At its most basic without a full lecture:

Gerunds are used when actions are real, fixed, or completed. "I enjoy cooking."

Infinitives are used when actions are unreal, abstract, or future: "He wants to swim."

...........but there are loads of exceptions!

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