The speaker thinks human heuristics are good enough that most thoughts entering conscious awareness are at least plausible candidates for truth.

“have such good heuristics that probably most of the things that show up even in our conscious mind rather than happening on the level of some kind of unconscious processing are at least the kind of things that could be true like I think you could think of this as like a chess engine you have some unbelievable number of possible next moves you have some heuristics for picking out which of those are going to be the right ones and then gradually you kind of have the chess engine think about it”