Some recent statements reportedly made in private by Donald Trump have prompted renewed interest in a question I raised months ago: Is Trump just a bald-faced liar or does he actually believe some or many of the falsehoods that he constantly spouts? I concluded that mostly Trump is just a liar, although in a response to a comment I modified that conclusion with the observation that the line between mendacity and delusion isn’t always clear. A good liar often manages to half-convince himself of his own lies.

Trump has reportedly asserted that he doubts that the voice on the notorious Access Hollywood tape, in which Trump bragged about his ability to grab women’s crotches with impunity, was actually his. But Trump hasn’t expressed his doubts publicly. If his revisionism serves no public, political purpose, does it not seem likely that his doubts may be genuine? And, since there is no rational basis for doubting the veracity of the tape, doesn’t it seem likely that our president is delusional? Similarly, it is reported that Trump in private has once again challenged the authenticity of President Obama’s birth certificate. And, just to add to credible doubts about his in-touchness with reality, Trump has tweeted credence to a ridiculous conspiracy theory holding that TV commentator Joe Scarborough was responsible for the murder of one of his interns.

The question of mendacity vs. delusion isn’t just a matter of curiosity. If Trump is truly prone to delusional fits, then his capacity for rational judgment—an essential quality in, say, an international crisis—is in serious doubt. There would be a strong case for his removal from office for incapacity via the 25^th amendment to the Constitution.

I’m sorry to poke a hole in the case for a 25^th amendment solution, but I still think Trump is mostly just a liar, not delusional. But he’s a special kind of liar. An ordinary liar is calculating.  He knows and in his own way cares about the truth: he cares enough to generally try to make his lies credible. Trump is extraordinary in that the truth is simply irrelevant to him; it doesn’t in any way constrain what he says. He says whatever serves his purposes; the truth or falsity or credibility of his words simply don’t matter.  So, if it makes him feel good to renew his birther claims, he will do so.

Don’t get me wrong. I’m not arguing that there is no reason to doubt Trump’s rationality. His impetuousness, his emotional immaturity, his extreme ego sensitivity and his gross over-estimation of his own abilities are all grounds for worry. I just don’t think that his near-daily output of falsehoods provides evidence of true delusion.