It is an enduring mystery about Donald Trump that, for a guy who lolls around all day eating cheeseburgers, he appears in good health. As far as we know he doesn’t work out. He is given to fits of temper and is consumed by large hatreds. He has the most stressful job in the world and all his former aides are being busted for fraud. And yet he will probably outlive us all. One of the most aggravating things about narcissists of course is that they sleep very well. If the president, at 72, still has a baby-like sheen, one can assume it comes in part from his failure to feel shame or self-doubt.

Of everything about the man, this is perhaps the hardest to stomach, and yet one continues to have one’s hopes raised. This week, the Democratic congressman Richard Neal evoked an obscure provision in the tax code to formally request that the US tax authorities release six years of Trump’s returns. We should know better by now; we’ve been here before. Still, up went the flare of adrenaline. This was the one, finally, that would nail him.

House Democrats formally demand Trump's tax returns from IRS Read more

This feeling has less to do with the hope of exposing Trump for wrongdoing, it seems to me, than with the dream of achieving some kind of catharsis. Confronted with his lies, Trump denies and slides to the side, as he immediately did when asked about the tax returns. (In fact, he revived his defence that, years after the first request for disclosure was made, he was still being audited.) A lie like this might, under normal circumstances, be an indication of some internal panic on the part of the liar, but from Trump one gets no such sense. This same week, he placidly insisted on the absurdly disprovable claim that his father was born in Germany (Fred Trump was born in New York).

Instinctively, one knows that to confront a compulsive liar with their own delusions is an extremely dangerous thing. The few times I have known those who told wild lies, what started out as amusing or baffling at some point became deeply sinister, not least because a childish refusal to admit error triggers in those being lied to an equally childish desire for revenge. Contained in the hope of the Trump tax returns is the conviction that finally, in black and white, he will be forced to confront reality.

This seems to me the biggest delusion of all. It is right and proper to be furious when his former fixer/attorney Michael Cohen tells Congress that he believes Trump undervalued his assets to cheat on his tax return, and to rage after reading the New York Times investigation into what might be described, mildly, as accounting irregularities in Trump’s empire. But to expect the man himself to give us closure by conceding an inch? He’s never going to deliver. There will be no closure. Political anger is righteous and useful, but it’s a pitiful waste of time and emotion for us to expect remorse to be expressed by a man who apparently has no conscience at all.

• Emma Brockes is a Guardian columnist