He argued brillantly against Aristotle’s world-picture and on several important matters in physics he took up positions which are commonly thought not to have been espoused until Galileo’s day. For example, Philoponus attacked Aristotle’s theory that the earth andthe heavens are separate realms which need radically different physical principles to explain them. Philoponus denied that stars were eternal and unchangeable and this rejected the whole basis of what was to become standard medieval cosmology.
He carefully demolished Aristotle’s arguments, showing that they did not make sense in themselves andmoreover that they contradicted other things which Aristotle had said. Most significantly, Philoponus made extensive use of personal observation and even experiment to support his own physical theories
Philoponus‘ own theory of falling bodies was not quite right, but the experiment he describes here (which does at least refute Aristotle’s view) was heralded as momentous scientific breakthrough when it was repeated in the seventeenth century
Philoponus was the last of his kind: as far as one can tell, nobody in Western Europe practised his sort of analysis of nature again until the fourteenth century.
[Anthony Gottlieb: The Dream of Reason. A History of Philosophy from the Greeks to the Renaissance. New York 2000. S. 385f.]