Every year, those of us who graduated from our medical school in a particular year set meet in different parts of the world for reunions, and occasionally we have an international reunion. This year's meeting was in Toronto, Canada, and I was asked to give a virtual presentation. I have given presentations at previous reunions and usually try to make them light, enjoyable and memorable. I intended to do the same this year, especially since I spoke about AI at a previous meeting. However, as I prepared this presentation, something had changed. The people developing AI — including senior executives and researchers in the technology industry — were increasingly warning about its potential risks. Some have even suggested that sufficiently advanced AI could pose an existential threat to humanity. I therefore had to reconsider the presentation. I began to feel rather like Cassandra, the prophetess of Greek mythology, who was condemned to predict the future but never to be believed. But p...