The divide between AI fantasists and doomers is growing. The fantasists believe AI will turbocharge growth and create a utopian world of abundance. The doomers believe it poses an existential threat to humanity and that, before killing us, it will lead to mass unemployment and a world of pervasive surveillance and alternative realities. Who is right? And can governments do anything to mitigate the risk of catastrophe?

AI enthusiasts gush about the technology’s implications for productivity. Anthropic CEO Dario Amodei has predicted that US GDP growth will rise from today’s paltry 2% to 10–15%. Elon ...