Excerpts from Medieval Thinkers

Abu Nasr Muhammad ibn al-Farakh al-Farabi or Alfarabi (c. 878-950)

Ibn Sina or Avicenna (c. 973-1037) was a sort of universal genius, known first as a physician. To his works on medicine he afterward added religious tracts, poems, works on philosophy, on logic, as physics, on mathematics, and on astronomy. He was also a statesman and a soldier.

On Medicine, c. 1020 (from Medieval Sourcebook)

Medicine considers the human body as to the means by which it is cured and by which it is driven away from health. The knowledge of anything, since all things have causes, is not acquired or complete unless it is known by its causes. Therefore in medicine we ought to know the causes of sickness and health. And because health and sickness and their causes are sometimes manifest, and sometimes hidden and not to be comprehended except by the study of symptoms, we must also study the symptoms of health and disease. Now it is established in the sciences that no knowledge is acquired save through the study of its causes and beginnings, if it has had causes and beginnings; nor completed except by knowledge of its accidents and accompanying essentials. Of these causes there are four kinds: material, efficient, formal, and final.

Material causes, on which health and sickness depend, are--- the affected member, which is the immediate subject, and the humors; and in these are the elements. And these two are subjects that, according to their mixing together, alter. In the composition and alteration of the substance which is thus composed, a certain unity is attained.

Efficient causes are the causes changing and preserving the conditions of the human body; as airs, and what are united with them; and evacuation and retention; and districts and cities, and habitable places, and what are united with them; and changes in age and diversities in it, and in races and arts and manners, and bodily and animate movings and restings, and sleepings and wakings on account of them; and in things which befall the human body when they touch it, and are either in accordance or at variance with nature.

Formal causes are physical constitutions, and combinations and virtues which result from them.

Final causes are operations. And in the science of operations lies the science of virtues, as we have set forth. These are the subjects of the doctrine of medicine; whence one inquires concerning the disease and curing of the human body. One ought to attain perfection in this research; namely, how health may be preserved and sickness cured. And the causes of this kind are rules in eating and drinking, and the choice of air, and the measure of exercise and rest; and doctoring with medicines and doctoring with the hands. All this with physicians is according to three species: the well, the sick, and the medium of whom we have spoken.


From: Charles F. Horne, ed., The Sacred Books and Early Literature of the East, (New York: Parke, Austin, & Lipscomb, 1917), Vol. VI: Medieval Arabia, pp. 90-91.

Scanned by Jerome S. Arkenberg, Cal. State Fullerton. The text has been modernized by Prof. Arkenberg.

Ibn Rushd or Averroës (1126-1198)

On the Harmony of Religions & Philosophy, c. 1190 (from Medieval Sourcebook)


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.

Hence, for a believer in the Law and a follower of it, it is necessary to know these things before he begins to look into creation, for they are like instruments for observation. For, just as a student discovers by the study of the law, the necessity of knowledge of legal reasoning with all its kinds and distinctions, a student will find out by observing the creation the necessity of metaphysical reasoning. Indeed, he has a greater claim on it than the jurist. For if a jurist argues the necessity of legal reasoning from the saying of God: "Wherefore take example from them O you who have eyes" [Qur'an 59.2], a student of divinity has a better right to establish the same from it on behalf of metaphysical reasoning.

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.


From: 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, 122-131, 204-229, 242-249, 260-283, 300-308.

Scanned in by Jerome Arkenberg, of CSU.