Abu Bakr Muhammad b. Zakariya ar Razi (865-925) was perhaps the greatest freethinker in the whole of Islam. He was the greatest physician in the Islamic world, and one of the great physicians of all time. He wrote over two hundred books on a wide variety of subjects. His greatest medical work was the monumental encyclopaedia al Hawi, on which he worked for fifteen years. Ar Razi was a thorough empiricist, and not at all dogmatic. This is evident from his extant clinical notebook, in which he carefully recorded the progress of his patients, their maladies, and the results of the treatment. He wrote one of the earliest treatises on infectious diseases—smallpox and measles.
But what earned Ar Razi universal condemnation from Muslims for blasphemy were his views on revealed religions. He saw no possibility of a reconciliation between philosophy and religion. In two heretical works, one of which may well have influenced the European freethought classic De Tribus Impostoribus, Ar Razi gave vent to his hatred of revealed religions. Ar Razi’s heretical book On Prophecy has not survived, but we know that it maintained the thesis that reason is superior to revelation, and salvation is only possible through philosophy. The second of Ar Razi’s heretical works has partly survived in a refutation by an Ismaili author. Here are its principal (and audacious) theses:
All men are by nature equal and equally endowed with the faculty of reason that must not be disparaged in favour of blind faith; reason further enables men to perceive scientific truths in an immediate way. The prophets—these billy goats with long beards, as Ar Razi disdainfully describes them—cannot claim any intellectual or spiritual superiority. These billy goats pretend to come with a message from God, all the while exhausting themselves in spouting their lies, and imposing on the masses blind obedience to the "words of the master." The miracles of the prophets are impostures, based on trickery, or the stories regarding them are lies. The falseness of what all the prophets say is evident in the fact that they contradict one another: one affirms what the other denies, and yet each claims to be the sole depository of the truth; thus the New Testament contradicts the Torah, the Koran the New Testament. As for the Koran, it is but an assorted mixture of "absurd and inconsistent fables," which has ridiculously been judged inimitable, when, in fact, its language, style, and its much vaunted "eloquence" are far from being faultless. Custom, tradition, and intellectual laziness lead men to follow their religious leaders blindly. Religions have been the sole cause of the bloody wars that have ravaged mankind. Religions have also been resolutely hostile to philosophical speculation and to scientific research. The so-called holy scriptures are worthless and have done more harm than good, whereas the "writings of the ancients like Plato, Aristotle, Euclid, and Hippocrates have rendered much greater service to humanity."
"The people who gather round the religious leaders are either feeble-minded, or they are women and adolescents. Religion stifles truth and fosters enmity. If a book in itself constitutes a demonstration that it is true revelation, the treatises of geometry, astronomy, medicine and logic can justify such a claim much better than the Quran [the transcendent literary beauty of which, denied by Razi, was thought by orthodox Muslims to prove the truth of Muhammad’s mission]."
In his political philosophy, Ar Razi believed one could live in an orderly society without being terrorized by religious law or coerced by the prophets. Certainly the precepts of Muslim law, such as the prohibition of wine, did not trouble him in the least. (As noted already, Ar Razi felt that it was through philosophy and human reason that human life could be improved, not through religion.)
Finally, Ar Razi believed in scientific and philosophical progress, that the sciences progressed from generation to generation. He held that one must keep an open mind, and not reject empirical observations simply because they do not fit into one’s preconceived scheme of things. Ar Razi believed that his own contributions to the sciences would be superseded by even greater minds than his.
It is clear from the preceding account that Ar Razi’s criticisms of religion are the most forceful that appeared in the entire Middle Ages, whether European or Islamic. His heretical writings, significantly, have not survived and were not widely read; nonetheless they are a witness to the remarkably tolerant Islamic culture and society in which Ar Razi lived (a tolerance lacking in other periods and places).
We believe that Ar Razi upholds the values that we cherish: rationalism, religious skepticism, belief in science, the application of human reason to the problems besetting mankind, empiricism, a lack of dogmatism, and distrust of blind tradition. These qualities, so rare at any time, are so much the more remarkable from someone living in the early years of the 10th century, and are just what we need if Islamic society is to regain its former glory.