"We have as much proof that his memories are false as he might that they are true."

This isn't really how evaluating evidence works is it? Suppose I told you that I have a magic flying carpet but I am unable to let you see ever it. You have as much evidence that I am lying as that I am telling the truth. It is still very likely that I am lying, because of all the other data you have available on the plausibility of magic flying carpets.