Comment by tovej

Easy, humans can synthesize new facts using logic and context. And the conclusions can be checked against the real world to check that the reasoning was correct.

Or another way: reasoning is a socially constructed concept, developed by humans. Humans therefore have defined reasoning, and must therefore know how to reason.

Or a third way: I experience reasoning, you experience reasoning. I am currently reasoning. You are currently reasoning. I am human, as are you. Therefore humans reason.