A friend of mine whom I’ve kept in contact with over text message (we live in different countries) does not believe the Covid-19 pandemic is real. He is taking precautions and practicing social distancing, but he told me that he believes Covid-19 is a political, worldwide hoax to control people. I was flabbergasted to hear this. I tried to explain to him that the disease is no hoax: I know doctors fighting it, I know people who have contracted the virus and so on. But nothing has persuaded him.

Should I cut off my relationship with him or continue to talk to him? It is exhausting to argue with someone who believes in a conspiracy theory. I don’t feel I would lose much by cutting off ties with him, but how much of a responsibility do I have to make him understand the truth? It feels bigger than just our relationship. Name Withheld

Your friend believes in an astonishingly complex conspiracy. It would involve a secret deal between Donald Trump and Xi Jinping and dozens of other political leaders on every habitable continent — people who haven’t managed to coordinate their plans on lots of other important matters, like climate change. It would involve doctors in Geneva at the World Health Organization, in Atlanta at the C.D.C. and in hospitals all around the world conspiring with data scientists at Johns Hopkins to produce a fantastic flow of fake information. Or, if your friend thinks that everything those politicians and scientists and health workers appear to be saying is itself made up, it would require an even more amazing capacity on someone’s part to control the media and the internet. And what possible purpose could it serve? You might as well propose that we are all living in the Matrix — though if we are, it isn’t just the pandemic that’s imaginary.

Now, I suppose that there’s a remote possibility that your friend suffers from clinical paranoia and needs professional help. If that’s what’s going on, there’s little you can do from over here. No harm in keeping in touch, but no point in exploring his delusions, either.