Foolish is commonly followed by of before a person or action, and by to before an infinitive. Other prepositions usually belong to separate phrases rather than the adjective itself.
Use foolish of someone to describe behaviour, and foolish to do something for actions. Foolish for can describe suitability or excess in some contexts. In, by, and many uses with to are usually separate adjunct phrases, not fixed combinations with foolish.
These forms are not interchangeable. Choose the construction by meaning, not by which preposition appears most often.
Use foolish of before the person whose action is judged.
Use foolish to before an infinitive to describe an unwise action.
Use foolish for when something is inappropriate for a purpose or person.
The same subject can take different constructions because each sentence answers a different question.
Some combinations appear in real text but do not mean what learners often assume.
By usually introduces manner or comparison, not the adjective complement.
✕ He was foolish by trusting everyone. ✓ He was foolish to trust everyone.Of introduces the person; to introduces the action.
✕ It was foolish to him to lie. ✓ It was foolish of him to lie.In can introduce an activity, but it is not the normal complement after foolish.
✕ She is foolish in this plan. ✓ She is foolish to support this plan.Choose the expression that matches the intended meaning.
Paste the complete sentence below. Linguix checks the preposition together with grammar, spelling, punctuation, and style.
Yes. Foolish of someone is a standard way to criticise a person's behaviour.
Yes. Foolish to plus a verb is very common for describing an unwise action.
Not usually as a fixed adjective pattern. By often introduces another idea such as comparison or method.
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