WHAT is it about the letter X — its shape, perhaps, or its sound — that immediately projects mystery and suspense? Wilhelm Konrad von Röntgen understood its power when he branded his new invention, which could see inside objects, the X-ray. And it worked. We have been fascinated by X-rays ever since. The technology has been used to sell everything from golf balls to laundry detergent; people have hosted X-ray parties; and X-rays of Mohammed Ali’s jaw and Marilyn Monroe’s chest have sold for thousands of dollars.

In Thinking Allowed (Radio 4, Tuesday of last week), Laurie Taylor will often investigate how a technology may affect the way in which we conceptualise the world and thus also our language; and, in last week’s episode, two medical technologies were the focus of his attention. The promise of seeing beyond the surface, to reveal hidden layers, has profoundly changed the way in which we can investigate the material world, but also prompts a way of thinking about human psychology. Meanwhile, the stethoscope offers a complementary service, listening into the heart of things in a procedure curiously distant and yet also intimate.

Thinking must, of course, be allowed. But there are times when the manner of discourse which Free Thinking (Radio 4, Friday of last week) espouses in its title can become mere thinking aloud. The headline of last week’s episode, Crisis and Decision, promised an erudite investigation of how we might “make sense of the present moment, and where do we go from here”. Gathered in Matthew Sweet’s studio was an embarrassing richness of philosophers primed to excoriate our narcissistic and wasteful age.

Yet Sweet’s plan immediately fell apart, as none of his guests appeared willing to contribute to a list of crises that might then be analysed. Academics, like politicians, prefer their own questions, and prefer to answer them in a jargon that rapidly becomes incomprehensible. All respect to Melvyn Bragg, who herds his academic cats with such firmness on In Our Time.

I also wonder whether some forms of thinking are freer than others. Clare Chambers, a professor of political philosophy, might, in another context, have attracted the attention of Ofcom as she sought to present objective critical rationalism as the only antidote to the current post-truth culture — and then proceeded to reel off the examples of Donald Trump, Brexit, and Sir Keir Starmer. Some small recompense was made by a Freud expert, Mark Solms, who seemed to be blaming everything on our own personal selfishness.

Of course, the crisis that rules them all, to which all other crisis-mongers defer, is the climate. In Radio 4’s heavily plugged comedy Randy Feltface’s Destruction Manual (Radio 4, Saturday), our anti-heroic presenter is a purple puppet who tells darkly humorous gags about the various ways in which we are destroying the planet. Evidently, the puppet has a following on Netflix and TikTok, where the visual conceit is more obvious; but the audience for such dark humour must lie within a narrow corridor between those who can’t see the funny side and those who can’t see the problem.