Ptolemy (c. AD 100–70)

The astronomer Ptolemy was one of the leading scientific figures of Graeco-Roman antiquity. His contributions to philosophy lie in his reflections on scientific activity. In knowledge, he distinguishes a perceptual stage, which provides the natural link between knowledge and things, from a further, rational stage, governing the transition to science. The move towards science consists of the progressive distinction between concepts, initially acquired through experience and methodical observation. Many components of his thought are derived from earlier philosophy, but he excludes those aspects which bear on more general philosophical issues.