The 18-time world champion won one match in five against the tech firm’s AlphaGo system in 2016. He is quitting because “even if I become the number one, there is an entity that cannot be defeated.” (Agence France-Presse)
Talking point: The South Korean player is the only human to have beaten the machine in tournament play, but the AlphaGo competing today isn’t the same as the one Lee faced. While the original was based on a database of human games, the current AlphaGo Zero mastered the game by practising against itself—it’s learning through active practice, like a person would. That’s made it even harder to beat. Game experts have said it’s making moves that humans wouldn’t, focusing on the centre of the board instead of the sides and corners.