It’s almost always the case when the president of the United States says, “I give you my word as a Biden,” that whatever he’s about to say is untrue.

Joe Biden’s incredible stories have finally generated more mainstream attention, particularly after he erroneously claimed to have gone to Ground Zero the day after Sept. 11 and stared into “the gates of hell.”

The president even got an extensive, excoriating fact check from CNN about all his false and exaggerated yarns.

So why does Biden do this? To understand the source of his constant flagrant departures from reality, it’s worth reverting to the late philosopher Harry G. Frankfurt’s analysis in his classic essay, “On Bull—-.”

“It is impossible,” Frankfurt writes, “for someone to lie unless he thinks he knows the truth. Producing bullshit requires no such conviction.” The person doing it cares about the facts only “insofar as they may be pertinent to his interest in getting away with what he says. He does not care whether the things he says describe reality correctly. He just picks them out, or makes them up, to suit his purpose.”

Frankfurt adds that the spinner of these tales “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, bull—- is greater enemy of the truth than lies are.”

What is Biden’s purpose? Self-valorization, of course — literally from the moment of his birth, which he has repeatedly mischaracterized. His stories are almost always supposed to be dramatic, moving and pointed, with Biden himself the center of the action.

The psychologist might have trouble disentangling Biden’s chip on his shoulder and sense of inadequacy from his excessive self-regard.

For instance, Biden’s classic, falsehood-laden fusillade at a New Hampshire campaign event in 1987 about his own brilliance and accomplishment as a student was disturbing, hilarious and, at the end of the day, pathetic.

Biden is a talker, and of the worst sort. It’s one thing to be a talented conversationalist, brimming with interesting and funny things to say.

Or a gifted speaker, whose after-dinner remarks never leave anyone dissatisfied.

Biden, on the other hand, is notable only for the amount of his talking, not its quality. Biden easily could be that guy who never shuts up at the end of the bar who says he had tickets on the 50-yard line of the Philadelphia Eagles game when he really was in the upper deck behind one of the endzones.

Biden wasn’t particularly careful when he was a much younger man in the U.S. Senate. Otherwise, he wouldn’t have blown himself up in 1987 cribbing from British politician Neil Kinnock to say false things about his own family background.

Now, he’s older. That means some of these stories have been related over and over, and stories never get worse in the retelling, only better. On top of this, he’s almost certainly more genuinely confused about timelines and facts than he was in his prime.

Now, his malarkey, to use his term from his vice-presidential debate with Paul Ryan back in 2012, is more obvious and discrediting than ever. His words as a Biden are usually insufferable and, at times, complete bull—.