I don't get something about this statement...

now this is reminding me of someone one of my professors told me about. Took this to the next level, "I think, therefore i am" but since all you can prove to your mind is that you think, because we couldn't tell if reality was some sort of vivid hallucination, you cannot prove to anyone else that you exist, or that anyone else exists to you. Doesn't mean they don't exist, just unproveable if you allow that everything could be a illusion perpetrated by some sort of demon(i think he was pretty religious so, if someone is duping humanity, it'd be a demon). Which more or less plays into the matrix.