René Descartes (c.1596–1650), was a French philosopher, mathematician, and scientist, and the “father of modern philosophy”. As this title shows, René Descartes is considered one of the greatest and most influential philosophers of all time, due to his contributions to modern Western philosophy and his break from the traditional Scholastic-Aristotelian philosophy widespread in his day. But were Descartes’ ideas original?

I argue in this piece that Descartes was largely influenced by Muslim thinkers, especially Abu Hamid al-Ghazali (c.1056–1111), the great Muslim jurist, theologian, philosopher, and mystic.

The question of al-Ghazali’s influence on Descartes has previously drawn the attention of several scholars. For example in A History of Muslim Philosophy (1963), M. M.Sharif mentions a variety of similarities. Although, according to him, there is no direct evidence that al-Ghazali’s Deliverance had been translated into Latin by Descartes’ time, he asserts that the ‘‘remarkable parallel’’ between it and Descartes’ Discourse on the Method renders it ‘‘impossible to deny its influence.’’

Also Catherine Wilson took up the topic in her contribution to the more recent History of Islamic Philosophy (1996), where she cites V. V. Naumkin (1987) as claiming historical proof that Descartes did actually read al-Ghazali.

Now let us indulge in some of Descartes’ most prominent philosophical ideas.

The essence of Descartes’ philosophy is that ‘the greatest care must be taken not to admit anything as true which we cannot prove to be true’. So to have a strong and stable foundation, Descartes made himself doubt everything that he was able to doubt, all of which ended in doubting sensory data. and ideas that come from reason.

Descartes held that the entire scope of of sense perception could be doubted , due to the reason that what is presented to humans by their senses might as well be as insubstantial as dreams, illusions, and hallucinations.

Descartes argued that the source of these insubstantial presentations may be an evil demon with the purpose of deceiving humans, and not from a good God. Now even the existence of God could be doubted. But how does Descartes overcome this overwhelming doubt? He maintained that the only thing that he could not doubt, was the fact that he doubts. He continued to state that to doubt is to think, but he cannot think if he does not exist. Descartes explains in his ‘Discourse of the Method’:

I saw… that from. the mere fact that I thought of doubting the truth of other things, it followed quite evidently and certain that I existed.

He continues in part four of the Discourse:

But immediately upon this I observed that, whilst I wished to think that all was false, it was absolutely that I, who thus thought, should be somewhat and as I observed that this truth, I think hence I am, was so certain and of such evidence, that no ground of doubt, however extravagant could be alleged by the skeptics capable of shaking it, I concluded that I might, without scruple, accept it as the first principle of the philosophy of which I was in search.

So now Descartes has established the foundation of his philosophy which can be summed in the famous latin phrase, Cogito ergo sum, (I think, therefore I am). Descartes continues after establishing that he surely exists to examine his own nature and the nature of other things, which led him to establish his theory of dualism, known today as Cartesian dualism.

Descartes establishes that the mind and body are distinct and therefore separable. He explains that the mind is a thinking substance, and that depends on nothing but God, and that the body is a different kind of substance because it depends on things other than God.

In Descartes’ Meditations, several themes and ideas are presented, which are mainly centered around the essence and existence of matter, the self, and God. And from these ideas several issues must be examined, the method of doubt and skepticism, dualism, and the existence of God.

Now let us discuss the originality of these ‘Cartesian’ ideas. Probably the most comprehensive representation of al-Ghazali’s matured thought can be found in his magnum opus, Revival of Religious Sciences. And his Persian abridgment of the Revival, Alchemy of Happiness, is divided into four sections dealing with, knowledge of self, knowledge of God, knowledge of the world as it really is, and knowledge of the next world as it really is.

This is roughly parallel to the order of topics treated by Descartes in his Meditations on First Philosophy, with the exception that any section on ‘knowledge of the next world as it really is’ is missing, and that, prior to ‘knowledge of self,’ which is treated in the Second Meditation, Descartes takes up, in the First Meditation, the issue of knowledge per se.

A much clearer comparable discussion of this last topic occurs not in the Alchemy but in the beginning of the Deliverance From Error, in a manner strikingly similar in both structure and content to Descartes’ discussion in the First Meditation.

In his Deliverance From Error, al-Ghazali reflects on his journey from skepticism to faith. Previous scholarship has actually interpreted this text as an anticipation of Cartesian positions regarding epistemic certainty.

In this autobiographical account al-Ghazali first reached absolute skepticism and doubted sensory evidence, since they were often deceiving. At first he began with temporarily suspending authority in the matters of faith, and rejected tradition (taqlid). al-Ghazali scrutinized all his cognitions and was completely empty of any knowledge. He also compared the conscious state of wakefulness with the dreaming state, al-Ghazali further explains:

Don’t you see that when you are asleep you believe certain things and imagine certain circumstances and believe they are fixed and lasting and entertain no doubts about that being their status? Then you wake up and know that all your imaginings and beliefs were groundless and insubstantial.

Then al-Ghazali references the viewing of a star to the deceitfulness of the senses. When we look at a certain star it appears to us to be no bigger than a coin, but in actuality it is bigger than the earth itself. We figure this out, by the power of the intellect, through geometric calculations. But al-Ghazali then doubts even mathematical and logical truths, since they could also be deceiving.

Here we can see the striking similarities between Cartesian doubt and the al-Ghazalian methodology. Descartes also rejected authority and custom and only relied on his own reasoning. Then like al-Ghazali, he also doubted sensory data, due to their ability to deceive. Descartes asks, what about things that we clearly perceive, such as our state of wakefulness or the fire in front of which we are sitting? Descartes also used the example of the dream here to showcase the ability of the senses to deceive.

Finally Descartes, like al-Ghazali, also doubted essential and mathematical truths by raising the following question:

Since I judge that others sometimes make mistakes in matters that they believe they know most perfectly may I not, in like fashion, be deceived every time I add two and three or count the sides of a square, or perform an even simpler operation, if that can be imagined.

Now let us examine the soul in al-Ghazalian metaphysics. Al-Ghazali distinguished between body and soul, according to him, the soul of the human being originates directly from God and that’s the reason why it is immaterial, immortal and more unique than the body or the rest of natural creation itself. The soul thus occupies a pivotal role in al-Ghazalian metaphysics. Without the soul the body is not complete and cannot function, al-Ghazali states:

The body is subject to dissolution as it was subject to being compounded of matter and form, which is set forth in the books. And from … verses and tradi- tions and intellectual proofs we have come to know that the spirit [the soul] is a simple substance, perfect, having life in itself, and from it is derived what makes the body sound or what corrupts it.

For al-Ghazali, the human being is both soul and body, he is at once both a physical being and a spirit, and the soul governs the body. But this dual nature human beings does not necessarily imply a dualism since the soul and the body are two aspects of one and the same entity. For him, the soul and the body are interdependent.

Now I am going to showcase some passages from the two great works of al-Ghazali and Descartes, Deliverance From Error, and Meditations, in parallel in which the similarities between the two are striking:

(Deliverance From Error)

For nearly ten years I assiduously cultivated seclusion andsolitude. During that time several points became clear to me, of necessity and for reasons I cannot enumerate — at one time by fruitionalexperience, at another time by knowledge based on apodictic proof, andagain by acceptance founded on faith. These points were that man isformed of a body and a heart.


Several years have now passed since I first realized how numerous were the false opinions that in my youth I had taken to be true, and thus how doubtful were all those that I had subsequently built upon them. And thus I realized that once in my life I had to raze everything to the ground and begin again from the original foundations, if I wanted to establish anything firm and lasting in the sciences. But the task seemed enormous, and I was waiting until I reached a point in my life that was so timely that no more suitable time for undertaking these plans of action would come to pass.

(Deliverance From Error)

So I began by saying to myself: “What I seek is knowledge of thetrue meaning of things. Of necessity, therefore, I must inquire into just what the true meaning of knowledge is.” Then it became clear to me thatsure and certain knowledge is that in which the thing known is made somanifest that no doubt clings to it, nor is it accompanied by thepossibility of error and deception, nor can the mind even suppose such apossibility.


I should withhold my assent no less carefully from opinions that are not completely certain and indubitable than I would from those that are patently false. For this reason, it will suffice for the rejection of all these opinions, if I find in each of them some reason for doubt.

(Deliverance From Error)

I then scrutinized all my cognitions and found myself devoid of any knowledge answering the previous description except in the case of sense-data and the self-evident truths. So I said: “Now that despair has befallen me, the only hope I have of acquiring an insight into obscure matters is to start from things that are perfectly clear, namely sense-data and the self-evident truths.”


But at least they do contain everything I clearly and distinctly understand. First, I know that all the things that I clearly and distinctly understand can be made by God such as I understand them.

(Deliverance From Error)

With great earnestness, therefore, I began to reflect on my sense-data to see if I could make myself doubt them. This protracted effort to induce doubt finally brought me to the point where my soul would not allow me to admit safety from error even in the case of my sense-data.Rather it began to be open to doubt about them and to say, “Whence comes your reliance on sense-data?”


But now, having begun to have a better knowledge of myself and the author of my origin, I am of the opinion that I must not rashly admit everything that I seem to derive from the senses, but neither, for that matter, should I call everything into doubt.

(Deliverance From Error)

The strongest of the senses is the sense of sight. . . . Sight also looks at a star and sees it as something small, the size of a dinar; then geometrical proofs demonstrate that it surpasses the earth in size.


But perhaps even though the senses do sometimes deceive us when it is a question of very small and distant things.

(Deliverance From Error)

Then sense-data spoke up, “What assurance have you that your reliance on rational data is not like your reliance on sense-data? Indeed, you used to have confidence in me. Then the reason-judge came along and gave me the lie. But were it not for the reason-judge, you would still accept me as true. So there may be, beyond the perception of reason, another judge. And if the latter revealed itself, it would give the lie to the judgments of reason, just as the reason-judge revealed itself and gave the lie to the judgments of sense. The mere fact of the nonappearance of that further perception does not prove the impossibility of its existence.”


Still there are many other matters concerning which one simply cannot doubt. For whether I am awake or asleep two plus three makes five.

(Deliverance From Error)

For a brief space my soul hesitated about the answer to that objection, and sense-data reinforced its difficulty by an appeal to dreaming, saying, “Do you not see that when you are asleep you believe certain things and imagine certain circumstances and believe they are fixed and lasting and entertain no doubts about that being their status?Then you wake up and know that all your imaginings and beliefs were groundless and unsubstantial. So while everything you believe through sensation or intellection in your waking state may be true in relation to that state, what assurance have you that you may not suddenly experience a state which would have the same relation to your waking state as the latter has to your dreaming, and your waking state would be dreaming in relation to that new and further state?” If you found yourself in such a state, you would be sure that all your rational beliefs were unsubstantial fancies.


Let us assume then, for the sake of argument that we are dreaming and that such particulars as these are not true: that we are opening our eyes, moving our head, and extending our hands. Accordingly, I will suppose not a supremely good God, the source of truth, but rather an evil genius, supremely powerful and clever, who has directed his entire effort at deceiving me.Moreover, I find myself faculties for certain special modes of thinking, namely the faculties of imagination and sensing. I can clearly and distinctly understand myself in my entirety without these faculties, but not vice versa: I cannot understand them clearly and distinctly without me, that is, without a substance endowed with understanding in which they inhere, for they include an act of understanding in their formal concept.

Now, is it possible that Descartes had direct contact with works of al-Ghazali? While it cannot currently be determined that Descartes definitely read al-Ghazali, it is a fact that translations of his works were available to Europeans during the 16th and 17th centuries, therefore it cannot it be ruled out. Careful analysis of Cartesian philosophy reveals that many of his ideas seem to have been influenced by Arab philosophy or Islamic theology.

Descartes’ method of doubt is strikingly similar to al-Ghazali’s. Al-Ghazali and Descartes have similarities in their reason for and manner of doubt, their use of doubt to establish a sound epistemological foundation, their appeal to divinity to guarantee this foundation, and their claim that this foundation is not subject to proof or demonstration, but rather is immediately perceived.

The influence of Islamic philosophy on Western philosophy is widely recognized today. However, the exact nature of this influence has not to date been fully explored. And because of this, al-Ghazali’s influence on modern European thought has not so far been fully appreciated. 

Mustapha Itani

Leave a Reply

Your email address will not be published. Required fields are marked *