If you could see me, could you be sure your eyes and ears were not lying to you? Could you be certain I was not a fragment of a paranoid delusion created by your subconscious?

Are you sure you're even awake right now? Are you sure that you've ever been awake? Are any of your senses evidently reliable?

Perceived reality can never be perfect evidence, and it's not possible to step outside of your own perceptions.

Evidence is just that. If you try really hard to achieve full epistemological rigour I think it's inevitable you'll wind up at the conclusion you don't know anything at all.