A Dutch mathematician, lawyer, and politician who lived from 1625 to 1672. He presided over the first true republic since Roman times. Today, he is considered one of the Netherlands' greatest statesmen, even though his end came at his own people's hands. De Wit was a disciple of Rene Descartes; this would lead to both his successes and his horrible death.
Johan de Wit was born in Dordrecht in 1625. He attended the Universiy of Leiden, but received his law degree from the University of Angiers in 1645. Sometime between 1645 and 1650, he wrote his principal mathematical work, Elementa curvarum linearum, which developed analytic geometry for conic sections. We get our basic terminology (e.g. directrix) and formulae for conic sections from this work.
Since the beginning of the Dutch Republic around 1580, a group of urban merchant families held most of the power, with a stadtholder from the House of Orange in charge of the military. In 1650, stadtholder William II attempted to coerce the Estates of Holland into giving him more power, sending troops into Amsterdam and barricading the Estates in their building. The attack failed when William suddenly died of smallpox, leaving a posthumous son.
The most populous of the Seven Provinces of The Netherlands, the County of Holland, decided not to elect a new stadtholder this time. Instead, they elected a new Assembly. De Wit was the leader of Dordrecht's delegation.
Meanwhile, England and the Netherlands found themselves increasingly at odds over trade. In addition, the Dutch controlled most of France's trade, not something to make Louis XIV friendly. Oliver Cromwell's Rump Parliament passed the first Navigation Act in 1651 to restrict trade with the Netherlands. This led to the First Anglo-Dutch War in 1652, and several naval defeats for the Dutch.
In 1653, Johan de Wit was elected to the highest office in Holland, that of Raadspensionaris ("Grand Pensioner"). Johan and his brother Cornelis guided the country for the next two decades. He negotiated the 1654 Treaty of Westminster, where the Netherlands accepted the Navigation Act. 1654 also saw de Wit sponsor an Edict banning members of the House of Orange from being stadtholder.
The 1665-1667 Second Anglo-Dutch War brought several great naval victories for The Netherlands, but a threatened French invasion brought them to the negotiating table early. The de Wits traded the New Netherland colony for the much more profitable Suriname. In 1667, the Estates made de Wit's edict "perpetual".
At home, de Wit was determined to preserve the republican form of government. It was vital that his protege/rival William not be given any chance to reassert a monarchy over The Netherlands. De Wit made himself young William III's tutor, trying to steer the prince away from Catholic monarchism and towards Protestant Republicanism (Only the anti-Catholic part took). In addiiton, instead of creating a national military which William would naturally lead, he tried to rely on provincial militias for the country's defense. But despite his opposition, The Estates-General made William Captain-General of a national force.
De Wit was a master politican who held off much greater rivals for decades. However, all of de Wit's political skills couldn't keep France, Sweden, England, Cologne, and Münster at bay when they all gathered against the Netherlands in 1672. Louis XIV led 120,000 soldiers into The Netherlands. The English overran the New Netherland colony in North America. William III was unable stop the French, and they occupied most of the country. They were only stopped by floods made from deliberately breaking dikes. In June, however, Admiral Michiel de Ruyter defeated the combined English and French navies (with the help of Cornelis de Wit).
De Wit's Cartesian rationalism did not take the unreason of the mob into account. The people assumed that de Wit had betrayed them to the French, and mobs rampaged through several Dutch cities; pamphlets decrying his supposed treason circulated all over. The Dutch experiment with Republicanism seemed to be a failure; public sentiment was turned against de Wit. In times of crisis, people often choose strong leadership over rational leadership, and the office of stadtholder was resurrected on July 4, and given to William. Cornelis, accused of plotting to have Wiliam assassinated, was arrested in The Hague and tortured. Johan resigned his office two weeks later, on August 9.
A mob gathered outside the prison for Cornelis's trial. When he was acquitted (no evidence) on August 20, 1672, the mob went berserk. The crowd broke into the prison and tore both brothers to pieces. (This was the last political assassination in the Netherlands before Pim Fortuyn's 2002 murder.) William fought off the French, who had to content themselves with parts of the Spanish Netherlands.
Alexandre Dumas's 1850 novel The Black Tulip dramatizes the story's tragic conclusion. Although Dumas paints William as having engineered the de Witt brothers' destruction, history is unclear on what part, if any, William played. Dumas got many historical details wrong. The site of the murder, the Gevangenpoort, is now a museum.
The MacTutor History of Mathematics archive at
http://www-history.mcs.st-andrews.ac.uk/history/
Wold History at KMLA, The Dutch Republic, The First Era of Liberty (1650-1672)
http://stabi.hs-bremerhaven.de/whkmla/region/lowcountries/eralibi.html