can't help but + infinitive have no choice but + to infinitive

They have similar meaning, but when it comes to 'but', their grammar looks quite different. Why should infinitive be used after 'but' of the first one while to infinitive after the second 'but'?


2 Answers 2


You should not use a 'to'-infinitive in this sentence.

'To'-infinitives only follow certain verbs, and while 'help' is one of them, this is a different use of the word.

To explain - in the sentence "I got help to buy my house", 'help' means support or assistance.

But in sentences like "I could not help it", 'help' is defined as "stop yourself". For example, these essentially mean the same:

I could not help but laugh.
I could not stop myself from laughing.

"I can't help but..." is a particular idiom that draws meaning from this secondary use of 'help', and uses the conjunction 'but' to introduce something that happened contrary to your best efforts to stop yourself.


[ "cannot (help) but" + infinitive ] is an idiomatic structure. There's no broader rule about "but" here. The structure means roughly, "I cannot stop myself from doing X". I cannot think of any way to use "but" + infinitive other than with "can't".

In "have no choice but to" + infinitive, the rule is about the word "choice", not "but". After "choice", we use "to" + infinitive. Here, "but" means "other than", and doesn't affect the "to" + infinitive grammar.

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