Here is a useful way to distinguish atheism from agnosticism. The agnostic says, “There is insufficient reason to believe in God.” The atheist says, “There is sufficient reason to disbelieve in God.” (The theist says, “There is sufficient reason to believe in God.”) So construed, atheism entails agnosticism (but not conversely). In other words, atheism is a species, or special case, of the genus agnosticism.

We can avoid this result by interpreting the agnostic as saying, “There is insufficient reason to believe in God and there is insufficient reason to disbelieve in God.” So construed, agnosticism contradicts both theism and atheism. Theism and atheism are contraries but not contradictories. In other words, both can be false, but it’s not the case that both can be true.