One idea—symmetry—lies at the core of relativity theory, quantum mechanics, string theory, and a large portion of contemporary cosmology. Famous mathematician Ian Stewart tells the story of how this fascinating field of study first came to be in his book Why Beauty Is Truth. Stewart introduces us to figures like the young revolutionary Evariste Galois, who reshaped all of mathematics and founded the field of group theory only to perish in a pointless duel over a woman before his work was published, and the Renaissance Italian genius, rogue, scholar, and gambler Girolamo Cardano. Cardano stole the modern method of solving cubic equations and published it in the first significant book on algebra. Stewart also looks into the odd numerology of actual mathematics, where certain numbers have peculiar and unforeseen symmetry-related characteristics. He demonstrates how Wilhelm Killing found “Lie groups” with dimensions of 14, 52, 78, 133, and 248—groups whose very existence begs serious questions. The “octonionic” symmetries that could explain the cosmos’ basic existence are the last topic Stewart discusses in his description of the universe beyond superstrings.