Part of this is about how we draw a balloon around what 'you' are. If you are a talking ape, then that ape might be lying to itself. If you are a rationalist trapped in part of the brain of a talking ape, then you are just tricking another part of it's brain, which is entirely rational.
I absolutely love that idea. But I think a clearer way of explaining it is that we are talking apes who have picked up this blunt, rotting bone of rationality and are using it as any other tool to pursue the same old talking ape desires. While the means are rational, the ends aren't even close. Anyway, great point and lovely imagery!
We routinely deny, or act in spite of, inconvenient truths. We can recognize that there is no meaning to love beyond evolutionary and chemical triggers, yet we fight for it just as fervently. Nihilists write books about nihilism despite it's admitted pointlessness. We are as blind as our very genes which multiply and propagate themselves despite our executioner sun which grows daily above our heads, eventually to the point of consuming everything we know. By the very act of living and pursuing human concocted dreams and desires, we are in a constant denial of our situation.
Private Investigator? :-O