"Medieval Islamic science is thought to be its crown jewel. Yet what is meant by Islamic in this sense? Non-Muslims--Christians, Jews, and Zoroastrians--laid the foundations for this science. They relied mainly on Hellenic sources, but also Persian and Indian ones. Empirical findings risked being disregarded if they challenged the authority of the Koran in any way. In astronomy Islamic toponymics has of course left significant traces in the star map: Aldbeberan, Betelgeuse, Rigel. However, Islamic astronomy remained tied to Ptolemy’s Almagest. As such, it was incapable of freeing itself from geocentrism—there never was an Arab Copernicus. Algebra, to be sure, bears an Arabic name, but the basis of the discipline is Greek. Moreover, the "Arabic" numbers were originally Indian. It was the Indians who invented the all-important concept of zero.
What is usually termed Islamic philosophy consisted mainly of footnotes to the Greek thinkers. Philosophy always had a precarious situation, threatened by the perception of any encroachment on religious orthodoxy. Restrictions on freedom of thought are summed up by the concept of the "closing of the gate of Ijtihad." Somewhat loosely, one can render ijtihad as "freedom of thought." In the light of this event, which may have occurred as long as a thousand years ago, there is no longer any room for debate on many key questions. Today the Muslim intelligentsia, the ulema, is extraordinarily diffuse in its distribution. Yet the melancholy truth is that this body of thinkers has achieved uniformity on such subjects as homosexuality, the status of women, and the lending of money for interest. For a long time, there has been no room for debate on these matters."
And it goes on.