Swiss psychiatrist Elisabeth Kübler-Ross suggested that there are five stages of grief, but nobody has the attention span for that any more. We have leapt instead from stage one, denial — “there is no AI bubble”, to stage five, acceptance — “AI is a bubble and bubbles are great”.

The “bubbles are great” hypothesis has been advanced both in popular and scholarly books, but it was hard to ignore when Jeff Bezos, one of the world’s richest men, sought to draw a distinction between financial bubbles (bad) and industrial bubbles (less bad, maybe good). Bezos, after all, built one of the 21st century’s great businesses, Amazon, in the middle of a bubble that turned contemporaries such as Webvan and Pets.com into a punchline.

There is a solid theory behind the idea that investment manias are good for society as a whole: it is that without a mania, nothing gets done for fear that the best ideas will be copied.