Richard S. Westfall  is best known for his biography of a mathematician who was a key figure in what?
Isaac Newton Sir Isaac Newton {'1': ", '2': ", '3': ", '4': "} ( ; 25 December 1642 – 20 March 1726/27) was an English mathematician, astronomer, and physicist (described in his own day as a "natural philosopher") who is widely recognised as one of the most influential scientists of all time and a key figure in the scientific revolution. His book "Philosophiæ Naturalis Principia Mathematica" ("Mathematical Principles of Natural Philosophy"), first published in 1687, laid the foundations of classical mechanics. Newton also made pathbreaking contributions to optics, and he shares credit with Gottfried Wilhelm Leibniz for developing the infinitesimal calculus.
Isaac Newton in popular culture Isaac Newton was an English mathematician, natural philosopher, theologian, alchemist and one of the most influential scientists in human history. His "Philosophiae Naturalis Principia Mathematica" is considered to be one of the most influential book in the history of science, laying the groundwork for most of classical mechanics by describing universal gravitation and the three laws of motion. In mathematics, Newton shares the credit with Gottfried Leibniz for the development of the differential and integral calculus.