Galileo Galilei, the Italian astronomer and physicist, was born at Pisa. Although he created no systematic philosophy, his influence on the trend of modern philosophical thought is very marked. To it may be traced the definitive separation of physical science from philosophy, the abandonment of authority as a criterion of scientific truth, the distinction between objective and subjective qualities in observable phenomena, and the introduction (or reintroduction) of empirical and skeptical elements into philosophical investigations. The seventeenth-century revival of atomism and the removal of occult qualities from the concept of causation owed much to Galileo. His writings marked the beginning of an antimetaphysical movement in philosophy, exemplified in later times by Positivism and operationalism, and they remained relatively free from such concealed ontological assumptions as are to be found in some ostensibly nonmetaphysical systems; for example, in philosophical empiricism, mechanism, and phenomenalism. The events...