First published Fri Mar 4, 2005; substantive revision Wed May 10, 2017. Galileo Galilei (1564–1642) has always played a key role in any history of science and, in many histories of philosophy, he is a, if not the, central figure of the scientific revolution of the 17th Century. His work in physics or natural philosophy, astronomy, and the methodology of science still evoke debate after over 400 years.