Infinitesimal: How a Dangerous Mathematical Theory Shaped the Modern World
*Starred Review* Convinced that it opened the Royal Road through the mathematical thicket, seventeenth-century mathematician Evangelista Torricelli trumpeted the method of indivisibles. Yet in recounting how that method originated, provoked vigorous resistance, and finally prevailed, Alexander tells a story with implications far beyond mathematics. Premised on the definition of a line as a composite of countless infinitesimally small elements, the method of indivisibles opened the door to calculus. But it also subverted Aristotelian philosophical principles, so alarming defenders of the status quo. Alexander compellingly chronicles the clashes as Galileo squares off with Pope Urban VIII in Italy, and royalist Thomas Hobbes crosses swords with puritan John Wallis in England. Beyond what it teaches about mathematics, the intellectual combat illuminates the tempestuous birth of modernity. Alexander credits the champions of indivisibles with helping to usher in an era of progressive tolerance and democracy, and he indicts their foes as hidebound authoritarians. But as readers explore the personalities and life trajectories of the combatants, they will recognize complexities that do not fit into Alexander’s overall script: Bonaventura Cavalieri (one of the discoverers of indivisibles) was a cautious monk, while RenéDescartes (the father of modern philosophy) rejected the new mathematics. A bracing reminder of the human drama behind mathematical formulas. --Bryce Christensen