1. He is he.

2. He is him.
3. He is himself.
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Which one is grammatical?

Only #1 is correct.

Thank you for your help.

What about the following sentence?

4. He is not himself now.

That has a different sort of meaning ... that he is not acting normally right now.

To determine which of the statements is grammatically correct, we need to analyze the pronoun usage and their appropriate roles in the sentence.

1. "He is he." This statement is grammatically correct. It uses the pronoun "he" as both the subject and the predicate. This construction emphasizes the subject's identity.

2. "He is him." This statement is grammatically incorrect. It uses the pronoun "him" as the object in the predicate, which is incorrect since it should be in the subjective form like "he."

3. "He is himself." This statement is grammatically correct. It uses the reflexive pronoun "himself" to indicate that the subject and predicate refer to the same person. This construction emphasizes the subject's self-identity or identity in contrast to others.

In conclusion, both statements 1 and 3 are grammatically correct, while statement 2 is incorrect.