Sir Isaac Newton (1642–1727) and John Locke (1632– 1704) are Enlightenment philosophers. Thinkers during the European Enlightenment were confident that man could solve his problems — problems of government, morals, and society included — by the use of reason. Even the universe could be mathematically understood. Newton gave mathematical substance to this idea with the discovery of laws of motion and gravitation. John Locke ushered in the Enlightenment with the publication of An Essay on Human Understanding in 1690.