The news reports of Russian oligarch Roman Abromovich being poisoned at Ukrainian-Russian peace talks earlier this month yield a classic example of the late Donald Rumsfeld's “known unknowns”:

• We know that we do not know if the poisoning even happened, and, if it did happen, who is to blame.

• We know that we do not know if a recognized chemical weapon was used.

• We know that we do not know the sources behind this report, let alone their credibility.

We know these things because the article itself concedes as much:

The conditions of Mr Abramovich and the Ukrainian negotiators, who include Ukrainian MP Rustem Umerov, have improved since the incident on 3 March, the paper quoted sources as saying.

A source close to Mr Abramovich told the BBC he had suffered symptoms of suspected poisoning. They said he had now recovered and was continuing with negotiations to try and end the war in Ukraine.

Earlier on Monday, Mr Umerov tweeted that he was "fine" and urged people not to trust "unverified information".

The entirety of this BBC report, as well as a related story in the Wall Street Journal, is “unverified information”. Yet the media is putting it out there.

Which is why we should also know the imperative to trust nothing, and to verify everything.