Who was Fritz Haber?
A German chemist whose work both feeds much of the world and killed on an industrial scale — arguably the most morally difficult figure in the history of science, and a useful corrective to the idea that scientific achievement and moral standing travel together.
The achievement. With Carl Bosch he developed the Haber-Bosch process, which fixes nitrogen from the air into ammonia under high temperature and pressure. Before it, agriculture depended on finite natural nitrogen sources — manure, and guano and nitrate deposits that were being exhausted — and serious commentators predicted famine as populations grew.
Its scale is hard to overstate. Synthetic fertiliser derived from the process is commonly estimated to sustain roughly half the nitrogen in the human body worldwide, meaning several billion people alive today depend on it. It is also enormously energy-intensive, consumes a significant share of global natural gas, and the resulting nitrogen runoff is a major cause of water pollution and ocean dead zones.
The other half of his career. Haber was an ardent German patriot who directed the development and battlefield use of chemical weapons in the First World War. He personally oversaw the first large-scale chlorine attack at Ypres in April 1915, and argued that gas was no crueller than other weapons. His wife Clara Immerwahr, herself a chemist and an opponent of the work, died by suicide days afterwards, a connection that is frequently asserted and cannot be established with certainty.
He received the Nobel Prize in Chemistry for 1918, awarded amid international protest.
The ending is bitter. Haber was Jewish by birth, though he had converted. When the Nazis came to power in 1933 he was forced from his institute, left Germany, and died in Switzerland in 1934. Zyklon, a pesticide developed at his institute, was later adapted for use in the gas chambers, killing members of his extended family.
What he illustrates is that the same knowledge serves both purposes, and that intent does not control consequence.