This article uses forms of logical notation. For a concise description of the symbols used in this notation, see List of logic symbols.

In logic, the law of identity is the first of the so-called three classic laws of thought. It states that an object is the same as itself: A → A (if you have A, then you have A); While this can also be listed as A ≡ A (A if-and-only-if A,) this is redundant. Any reflexive relation upholds the law of identity. When discussing equality, the fact that "A is A" is a tautology.