Isaac Newton (1642-1727), the English genius, made his greatest contributions to original thought before the age of twenty-five, while at home in Lincolnshire escaping the great plague of 1665, a period of which he wrote: 'I was in the prime of age for invention.' Professor of Mathematics at Cambridge, an MP, Master of the Mind and President of the Royal Society, Newton, the author of Principia, one of the most important books in the history of science, was fascinated by calculus, the planets and the 'laws of motion', and, in keeping with his age, blurred the borders between natural philosophy and speculation: he was as passionate about astrology as astronomy and dabbled in alchemy, while his religious faith was never undermined by his scientific efforts.