In short Chalmers says that if we lived in Matrix, most of our beliefs about the external world would be true. I agree, because the Matrix hypothesis affects the overall conception of the world, but not specific beliefs about the world. An example: if two people fall in love in Matrix, outside of Matrix they may continue in love, proving that something happened there and that the difference between reality and simulation is pragmatically irrelevant. Other example: if reality is a hologram, a hypothesis treated by some scientists, is not that reality does not exist as some have claimed, but reality would not be what we think it was.