 At that time, the college's teachings were based on those of Aristotle, whom Newton supplemented with modern philosophers such as Descartes and astronomers such as Copernicus, Galileo, and Kepler.In 1665, he discovered the generalised binomial theorem and began to develop a mathematical theory that later became infinitesimal calculus.Soon after Newton had obtained his degree in August 1665, the University closed down as a precaution against the Great Plague of London.