If there's one question designed to irk everyone and stop them in their tracks it's 'How do you know?'
Its pseudo scientific gravitas has done more to destroy the West than anything else apart from yoga.
How do I know?
Exactly.
One can even do it to oneself to over self-check one's thoughts.
So the question is not just 'How do you know?' but also how does one deal with the question 'How do you know?' AND the questioner.
Unless the question is supposed to be an abstract one echoing the skeptic's challenge, "How is any knowledge whatsoever possible at all?", this question is unavailing because it has no context. If someone makes an assertion, say P, and someone else asks, "How do you know?" an answer might be given that depends on the specific content of P. Otherwise, without a P, we might indeed be reduced to responding with mere yogic breathing.
Maybe Peter Stott this is of interest to you and your query:
Chochmah is practical knowledge; how to do things: How to drive a car, how to tie your shoes—things you can learn and teach. Binah is knowledge of relationships: Putting A and B together, logical reasoning, even intuition. Da’at is experiential knowledge: How you know you’re alive, how you know God exists, how you know that 1+1 = 2. This knowledge cannot be proven, only experienced.
When you tell a child not to touch the stove because it’s hot and it burns, you’ve given him chochmah. When the child sees a pot on the stove and figures out that it might be hot too, he’s using his binah. However, when he puts his hand on the stove (Ouch!), he now has da’at!
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Article Foundations of a postmodern cybernetics based on Kabbalah