Enrico Fermi

The name most people meet first through the first controlled chain reaction, which sits at the centre of his reputation along with his work in neutron physics. What colleagues singled out, though, was something less dramatic: an economy of argument that made complicated problems manageable. He had a way of cutting a question down until it could actually be worked, and that habit, more than any single result, is what students carried away from him.

Born in Rome in 1901, he built his early work on disciplined study, careful method, and a willingness to press on assumptions that others accepted out of routine. Reading, correspondence and travel gave him points of comparison when deciding which problems were worth attacking. He also worked with his hands — in his account of it, observation and construction fed each other rather than sitting in separate compartments. Some of what looked at the time like modest clarification turned out to be the ground later work stood on.

Through the middle of his career the scope widened without the precision loosening. Publications, demonstrations and designs turned insights into techniques other people could reproduce; arguments with critics forced him to state more exactly what his claims did and did not cover. Students and collaborators took the method into neighbouring fields. Institutional posts gave him the platform to work at scale, and failed attempts were treated as tests that told him something useful about the next one.

In his last years, before his death in 1954, he leaned towards synthesis and teaching, passing on the core of the work without hardening it into doctrine. His notebooks and drafts show how provisional the finished results once were. The influence shows up less in citations than in a way of paying attention: think carefully, then act.