Falsehoods fly out of Donald Trump’s mouth with such unstoppable frequency that it’s tempting to describe him as a liar. Among the recent Trumpian untruths is his claim to have seen a video showing “thousands and thousands” of Muslim Americans cheering 9/11 in Jersey City, New Jersey, an event there is no record of, video or otherwise. Trump has also retweeted and vigorously defended the claim that 81 percent of whites who are murdered are killed by blacks (the actual number for last year is 15 percent). And he has asserted, contrary to fact, that the federal government is sending refugees to states with “Republicans, not to the Democrats.”

Yet the increasingly frequent tendency of Trump’s critics to label him a liar is wrongheaded. Trump is something worse than a liar. He is a bullshit artist. In his 2005 book On Bullshit, Harry G. Frankfurt, emeritus philosophy professor at Princeton University, makes an important distinction between lying and bullshitting—one that is extremely useful for understanding the pernicious impact that Trump has on public life. Frankfurt’s key observation is that the liar, even as he or she might spread untruth, inhabits a universe where the distinction between truth and falsehood still matters. The bullshitter, by contrast, does not care what is true or not. By his or her bluffing, dissimulation, and general dishonesty, the bullshit artist works to erase the very possibility of knowing the truth. For this reason, bullshit is more dangerous than lies, since it erodes even the possibility of truth existing and being found.

The contrast Frankfurt draws between lying and bullshit is sharp. “It is impossible for someone to lie unless he thinks he knows the truth,” Frankfurt observes. “Producing bullshit requires no such conviction. A person who lies is thereby responding to the truth, and he is to that extent respectful of it. When an honest man speaks, he says only what he believes to be true; and for the liar, it is correspondingly indispensable that he considers his statements to be false. For the bullshitter, however, all bets are off. … He does not reject the authority of the truth, as the liar does, and oppose himself to it. He pays no attention to it at all. By virtue of this, bullshit is a greater enemy of truth than lies are.”

Frankfurt’s analysis works extraordinarily well in explaining why Trump is so unfazed when called on his bullshit. Trump’s frequent response is to undermine the very possibility that the truth of his claims are knowable. When asked why there are no videos of “thousands and thousands” of Muslim-Americans cheering the 9/11 attacks, Trump told Joe Scarborough that 2001 was so far in the past that the evidence has disappeared. “Don’t forget, 14, 15 years ago, it wasn’t like it is today, where you press a button and you play a video,” Trump said in a phone interview on yesterday’s Morning Joe. “Fourteen, 15 years ago, they don’t even put it in files, they destroy half of the stuff. You know, if you look back 14, 15 years, that was like ancient times in terms of cinema, and in terms of news and everything else. They don’t have the same stuff. Today you can press a button and you can see exactly what went on, you know, two years ago. But when you go back 14, 15 years, that’s like ancient technology, Joe.”

This claim—that he’s telling the truth but that there can be no proof of it—is in some ways more insidious than the initial falsehood. It takes us to a post-truth world where Trump’s statements can’t be fact-checked, and we have to simply accept the workings of his self-proclaimed “world’s greatest memory.” In effect, Trump wants to take us to a land where subjectivity is all, where reality is simply what he says.