Among Muslims, Christians, and Jews of his era, Abu al-Walid Muhammad bin Ahmad bin Rushd (Averroes) was simply referred to as "the Commentator" for his commentary works on the Philosoper (Aristotle). He was mentored by the greatest Islamic philosophers of his time, especially Ibn Tufayl and Ibn Bajjah (Avempace). He lived and studied in Cordoba, Marrakesh, and Seville. He wrote on politics, physics, metaphysics, philosophy, jurisprudence, and religion, among others. But his most influential work was his commentaries on Aristotle's and Plato's books, which reintroduced the latter two back into Europe where he was referred to simply as "the Commentator." Most notably, Italian philosophers and scholars established a new school of thought called Averroism, named after him.
He firmly believed that philosophy (a term that also included the sciences back then) and religion were two different methods of expressing the same truth. He referred to this phenomenon as "the Double Truth." He was very critical of the religious scholars of his era (although he was a religious scholar himself; the chief justice of Corboda and Seville), and thus made many enemies among those scholars who took a quote out of one of his books, out of context, showing that he wrote that Venus was a god, and showed it to the caliph who then banished Averroes and ordered the burning of all his books. Fortunately, we still have many of his writings in our hands today.
The following are excerpts from his greatest books.
Translated by George F. Hourani
Praise be to God with all due praise, and a prayer for Muhammad His chosen servant and apostle. The purpose of this treatise is to examine, from the standpoint of the study of the Law, whether the study of philosophy and logic is allowed by the Law, or prohibited, or commanded - either by way of recommendation or as obligatory.
It cannot be objected: "This kind of study of intellectual reasoning is a heretical innovation since it did not exist among the first believers." For the study of juridical reasoning and its kinds is also something that has been discovered since the first believers, yet it is not considered to be a heretical innovation. So the objector should believe the same about the study of intellectual reasoning. (For this there is a reason, which it is not the place to mention here.) But most followers of this religion support intellectual reasoning, except a small group of gross literalists, who can be refuted by [sacred] texts.
But if someone other than ourselves has already examined that subject, it is clear that we ought to seek help toward our goal from what has been said by such a predecessor on the subject, regardless of whether this other one shares our religion or not. For when a valid sacrifice is performed with a certain instrument, no account is taken, in judging the validity of the sacrifice, of whether the instrument belongs to one who shares our religion or to one who does not, so long as it fulfils the conditions for validity. By "those who do not share our religion" I refer to those ancients who studied these matters before Islam. So if such is the case, and everything that is required in the study of the subject of intellectual syllogisms has already been examined in the most perfect manner by the ancients, presumably we ought to lay hands on their books in order to study what they said about that subject; and if it is all correct we should accept it from them, while if there is anything incorrect in it, we should draw attention to that.
When we have finished with this sort of study and acquired the instruments by whose aid we are able to reflect on beings and the indications of art in them (for he who does not understand the art does not understand the product of art, and he who does not understand the product of art does not understand the Artisan), then we ought to begin the examination of beings in the order and manner we have learned from the art of demonstrative syllogisms.
And again it is clear that in the study of beings this aim can be fulfilled by us perfectly only through successive examinations of them by one man after another, the later ones seeking the help of the earlier in that task, on the model of what has happened in the mathematical sciences. For if we suppose that the art of geometry did not exist in this age of ours, and likewise the art of astronomy, and a single person wanted to ascertain by himself the sizes of the heavenly bodies, their shapes, and their distances from each other, that would not be possible for him - for example to know the proportion of the sun to the earth or other facts about the sizes of the stars - even though he were the most intelligent of men by nature, unless by a revelation or something resembling revelation. Indeed if he were told that the sun is about 150 to 160 times* as great as the earth, he would think this statement madness on the part of the speaker, although this is a fact that has been demonstrated in astronomy so surely that no one who has mastered that science doubts it.
But it is hardly even necessary to use the example of the art of mathematics; for here is the art of the principles of jurisprudence [fiqh] and jurisprudence itself, both of which were perfected only over a long period of time. And if someone today wanted to find out by himself all the arguments that have been discovered by the theorists of the legal schools on controversial questions, about whcih debate has taken place between them in most countries of Islam (even if one excluded the West), he would deserve to be ridiculed, because such a task is impossible for him, apart from the fact that the work has been done already. Moreover, this is a situtaion that is self-evident not in the scientific arts alone but also in the practical arts; for there is not one of them that a single man can construct by himself. Then how can he do it with the art of arts, philosophy? If this is so, then whenever we find in the works of our predecessors of former nations a theory about beings and a reflection on them conforming to what the conditions of demonstration require, we ought to study what they said about the matter and what they set down in their books. And we should accept from them gladly and gratefully whatever in these books accords with the truth, and draw attention to and warn against what does not accord with the truth, at the same time excusing them.
From this it is evident that the study of the books of the ancients is obligatory by Law, since their aim and purpose in their books is just the purpose to which the Law has urged us, and that whoever forbids the study of them to anyone who is fit to study them - that is, anyone who unites two qualities, (1) natural intelligence and (2) legal integrity and moral virtue - is blocking people from the door by which the Law summons them to knowledge of God, the door of theoretical study that leads to the truest knowledge of Him; and such an act is the extreme of ignorance and estrangement from God, the Exalted.
... We can even say that a man who prevents a qualified person from studying books of philosophy, because some of the most vicious people may be thought to have gone astray through their study of them, is like a man who prevents a thirsty person from drinking cool, fresh water until he dies of thirst, because some people have choked to death on it. For death from water by choking is an accidental matter, but death from thirst is essential and necessary.
Since all this is now established, and since we, the Muslim community, hold that this divine Law of ours is true, and that it is this Law that incites and summons us to the happiness that consists in the knowledge of God, Mighty and Majestic, and of His creation, that [end] is appointed for every Muslim by the method of assent that his temperament and nature require. For the natures of men are on different levels with respect to [their paths to] assent. One of them comes to assent through demonstration; another comes to assent through dialectical arguments, just as firmly as the demonstrative man through demonstration, since his nature does not contain any greater capacity; while another comes to assent through rhetorical arguments....
Thus since this divine Law of ours has summoned people by these three methods, assent to it has extended to everyone.... This is clearly expressed in the saying of God, the Exalted, Summon to the way of your Lord by wisdom and by good preaching, and debate with them in the most effective manner [XVI, 125].
Now since this Law is true and summons to the study that leads to knowledge of the truth, we the Muslim community know indefinitely that demonstrative study does not lead to [conclusions] conflicting with what is given in the Law; for truth does not oppose truth but accords with it and bears witness to it.
* - Actually 109 times