Freeman Dyson is a legend in science. And he’s been friends and colleagues with the giants of 20th century physics, including Wolfgang Pauli, Richard Feynman and Robert Oppenheimer. At 93, he’s no longer an active scientist, but he’s still affiliated with Princeton’s famous Institute for Advanced Study. He says a bit of ignorance can lead to scientific breakthroughs, and he thinks we should abolish the PhD system, which often grinds down promising scientists.