I seldom see "whether" or "if" used after a positive verb. However, I think it is possible, like Examples 1 and 2.

Example 1

A: Tell me if your friend cheated.

B: I am sure whether/if he cheated. But I don't want to tell you.

Example 2

A: The program sucks. She should not enroll in it.

B: She knows whether/if the program is going to help her. Let her make her own decision.

1 Answer 1


Those particular B examples are unusual expressions, that would only be used after her knowledge had been called into question:

Does she even know whether he cheated?
She does know whether he cheated! She knows he did.

Does she even know whether the program will help her?
She certainly knows whether it will help her or not. She has good judgment.

But, if you're talking in general, rather than about a specific item of knowledge, you can definitely use whether/if after a positive verb-

She always knows whether to go ahead with a project or not.

  • In my opinion "I'm sure that he cheated" is the only possibility for No. 1 Commented Jan 29, 2022 at 17:04

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