Ibn Rushd (Averroës) (1126-1198) was one of the most important Islamic philosophers. He was wrote widely in medicine and jurisprudence, but he is best known for his work on the philosophy of Aristotle. The excerpt which follows is from one of his best known works. Written around 1190, he attempts to demonstrate that the study of philosophy is compatible with Islam.
We maintain that the business of philosophy is nothing other than to look into creation and to ponder over it in order to be guided to the Creator -- in other words, to look into the meaning of existence. For the knowledge of creation leads to the cognizance of the Creator, through the knowledge of the created. The more perfect becomes the knowledge of creation, the more perfect becomes the knowledge of the Creator. The Law encourages and exhorts us to observe creation. Thus, it is clear that this is to be taken either as a religious injunction or as something approved by the Law. But the Law urges us to observe creation by means of reason and demands the knowledge thereof through reason. This is evident from different verses of the Qur'an. For example, the Qur'an says: "Wherefore take example from them, you who have eyes" Qur'an 49.2. That is a clear indication of the necessity of using the reasoning faculty, or rather both reason and religion, in the interpretation of things. Again it says: "Or do they not contemplate the kingdom of heaven and earth and the things which God has created" Qur'an 7.184. This is in plain exhortation to encourage the use of observation of creation. And remember that one whom God especially distinguishes in this respect, Abraham, the prophet. For He says: "And this did we show unto Abraham: the kingdom of heaven and earth" Qur'an 6.75. Further, He says: "Do they not consider the camels, how they are created; and the heaven, how it is raised" Qur'an 88.17. Or, still again: "And (who) meditate on the creation of heaven and earth, saying, O Lord you have not created this in vain" Qur'an 3.176. There are many other verses on this subject: too numerous to be enumerated.

Now, it being established that the Law makes the observation and consideration of creation by reason obligatory -- and consideration is nothing but to make explicit the implicit -- this can only be done through reason. Thus we must look into creation with the reason. Moreover, it is obvious that the observation which the Law approves and encourages must be of the most perfect type, performed with the most perfect kind of reasoning. As the Law emphasizes the knowledge of God and His creation by inference, it is incumbent on any who wish to know God and His whole creation by inference, to learn the kinds of inference, their conditions and that which distinguishes philosophy from dialectic and exhortation from syllogism. This is impossible unless one possesses knowledge beforehand of the various kinds of reasoning and learns to distinguish between reasoning and what is not reasoning. This cannot be done except one knows its different parts, that is, the different kinds of premises.

One cannot maintain that this kind of reasoning is an innovation in religion because it did not exist in the early days of Islam. For legal reasoning and its kinds are things which were invented also in later ages, and no one thinks they are innovations. Such should also be our attitude towards philosophical reasoning. There is another reason why it should be so, but this is not the proper place to mention it. A large number of the followers of this religion confirm philosophical reasoning, all except a small worthless minority, who argue from religious ordinances. Now, as it is established that the Law makes the consideration of philosophical reasoning and its kinds as necessary as legal reasoning, if none of our predecessors has made an effort to enquire into it, we should begin to do it, and so help them, until the knowledge is complete. For if it is difficult or rather impossible for one person to acquaint himself single-handed with all things which it is necessary to know in legal matters, it is still more difficult in the case of philosophical reasoning. And, if before us, somebody has enquired into it, we should derive help from what he has said. It is quite immaterial whether that man is our co-religionist or not; for the instrument by which purification is perfected is not made uncertain in its usefulness by its being in the hands of one of our own party, or of a foreigner, if it possesses the attributes of truth. By these latter we mean those Ancients who investigated these things before the advent of Islam.

Now, such is the case. All that is wanted in an enquiry into philosophical reasoning has already been perfectly examined by the Ancients. All that is required of us is that we should go back to their books and see what they have said in this connection. If all that they say be true, we should accept it and if there be something wrong, we should be warned by it. Thus, when we have finished this kind of research we shall have acquired instruments by which we can observe the universe, and consider its general character. For so long as one does not know its general character one cannot know the created, and so long as he does not know the created, he cannot know its nature.

All things have been made and created. This is quite clear in itself, in the case of animals and plants, as God has said "Verily the idols which you invoke, beside God, can never create a single fly, though they may all assemble for that purpose" Qur'an 22.72. We see an inorganic substance and then there is life in it. So we know for certain that there is an inventor and bestower of life, and He is God. Of the heavens we know by their movements, which never become slackened, that they work for our benefit by divine solicitude, and are subordinate to our welfare. Such an appointed and subordinate object is always created for some purpose. The second principle is that for every created thing there is a creator. So it is right to say from the two foregoing principles that for every existent thing there is an inventor. There are many arguments, according to the number of the created things, which can be advanced to prove this premise. Thus, it is necessary for one who wants to know God as He ought to be known to acquaint himself with the essence of things, so that he may get information about the creation of all things. For who cannot understand the real substance and purpose of a thing, cannot understand the minor meaning of its creation. It is to this that God refers in the following verse "Or do they not contemplate the heaven and the earth, and the things which God has created?" Qur'an 7.184. And so a man who would follow the purpose of philosophy in investigating the existence of things, that is, would try to know the cause which led to its creation, and the purpose of it would know the argument of kindness most perfectly. These two arguments are those adopted by Law.

The verses of the Qur'an leading to a knowledge of the existence of God are dependent only on the two foregoing arguments. It will be quite clear to anyone who will examine closely the verses, which occur in the Divine Book in this connection. These, when investigated, will be found to be of three kinds: either they are verses showing the "arguments of kindness," or those mentioning the "arguments of creation, " or those which include both the kinds of arguments. The following verses may be taken as illustrating the argument of kindness. "Have we not made the earth for a bed, and the mountains for stakes to find the same? And have we not created you of two sexes; and appointed your sleep for rest; and made the night a garment to cover you; and destined the day to the gaining of your livelihood and built over you seven solid heavens; and placed therein a burning lamp? And do we not send down from the clouds pressing forth rain, water pouring down in abundance, that we may thereby produce corn, and herbs, and gardens planted thick with trees?" Qur'an 77.6-16 and, "Blessed be He Who has placed the twelve signs in the heavens; has placed therein a lamp by day, and the moon which shines by night" Qur'an 25.62 and again, "Let man consider his food" Qur'an 80.24.

This method is the right path by which God has invited men to a knowledge of His existence, and informed them of it through the intelligence which He has implanted in their nature. The following verse refers to this fixed and innate nature of man, "And when the Lord drew forth their posterity from the loins of the sons of Adam, and took them witness against themselves, Am I not your Lord? They answered, Yes, we do bear witness" Qur'an 7.171. So it is incumbent for one who intends to obey God, and follow the injunction of His Prophet, that he should adopt this method, thus making himself one of those learned men who bear witness to the divinity of God, with His own witness, and that of His angels, as He says, "God has borne witness, that there is no God but He, and the angels, and those who are endowed with wisdom profess the same; who execute righteousness; there is no God but He; the Mighty, the Wise" Qur'an 3.16. Among the arguments for both of themselves is the praise which God refers to in the following verse, "Neither is there anything which does not celebrate his praise; but you understand not their celebration thereof" Qur'an 17.46.

Source: Ibn Rushd:  On the Harmony of Religions and Philosophy, in Arabic Kitab fasl al-maqal, with its appendix (Damina). Appended is  an extract from Kitab al-kashf`an manahij al-adilla, published and translated  as: Averröes, The Philosophy and Theology of Averroes, trans. Mohammed Jamil-al-Rahman (Baroda: A. G. Widgery, 1921), pp. 14-19.