al-Ghazālī’s Dream Argument for Skepticism

Author: John Ramsey
Categories: Epistemology, Historical Philosophy, Philosophy of Religion, Islamic Philosophy
Word Count: 997

Right now you probably think that you are awake, that you are not asleep and dreaming. But do you know you aren’t dreaming?

French philosopher René Descartes (1596–1650) famously asked a question like this at the beginning of his Meditations on First Philosophy.[1] His answer was that since he couldn’t be certain he wasn’t dreaming, he didn’t know that he wasn’t dreaming, and since he didn’t know that, none of the beliefs he gained from his senses amounted to knowledge.[2]

The use of dreams to question whether we have knowledge and motivate skepticism—the view that we lack knowledge—has a richer history than contemporary philosophers often acknowledge. Persian-Muslim philosopher and legal scholar, Abū Ḥāmid al-Ghazālī (1058–1111) employed dreams to raise skeptical concerns about knowledge more than 500 years before Descartes did.

This essay explores the role of al-Ghazālī’s Dream Argument in his autobiographical al-munqidh min al-ḍalāl, or The Deliverance from Error, and how he uses it to raise doubts about whether we have any knowledge at all.


1. al-Ghazālīʼ’s Intellectual Journey Through Doubt

Al-Ghazālī frames Deliverance as a letter to an unnamed correspondent, who has asked about Al-Ghazālī’s intellectual journey from doubt to certainty (¶2).[3]

Al-Ghazālī begins his intellectual journey by recounting that, as a youth, he held with certainty many religious and cultural beliefs that he acquired from his Islamic upbringing. He began to doubt these beliefs when he realized that his beliefs differed from people who were raised Christian and Jewish.[4] He wishes to determine whether there was any truth to the beliefs routinely accepted in his community and, if true, to know them with certainty. So, he explains his steps towards regaining certainty.

As a first step, al-Ghazālī proposes and contemplates a standard that will help him tell whether he can know with certainty what he believes from his senses and from reason:

Then it became clear to me that sure and certain knowledge is that in which the thing known is made so manifest that no doubt clings to it, nor is it accompanied by the possibility of error and deception, nor can the mind even suppose such a possibility. (¶7)

Al-Ghazālī finds that many of his beliefs do not survive this test. Moreover, he begins to doubt his beliefs from sensory experiences because they are prone to error or correction from rational beliefs:

The strongest of the senses is the sense of sight. Now this looks at a shadow and sees it standing still and motionless and judges that motion must be denied. Then, due to experience and observation, an hour later it knows that the shadow is moving…. 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. In the case of this and of similar instances of sense-data the sense-judge makes its judgments, but the reason-judge refutes it and repeatedly gives it the lie in an incontrovertible fashion. (¶10)

So al-Ghazālī comes to doubt the certainty he earlier held regarding his sensory experiences. We have reasons to doubt that sensory experiences really represent reality because too often another sensory experience contradicts a prior experience—as happens when he observes the shadow an hour later. Or our use of mathematical proofs or other scientific methodology—as is the case with al-Ghazālī’s example of a star—provides a reason to doubt that our sensory experiences correspond to reality.

2. al-Ghazālī’s Dream Argument

Al-Ghazālī next considers beliefs based on reason—what he calls “primary truths”—such as the belief that 10 > 3 or the same claim cannot be simultaneously affirmed and denied (¶11). These beliefs do not fare any better than do beliefs from sensory experiences.

To help his reader understand why, al-Ghazālī personifies his senses so they can argue with him. The senses argue that since reason—which al-Ghazālī believes to be a “higher” ability than sensory experiences—can be used to doubt sensory experience, an even “higher” ability might be able to raise doubts about the beliefs of reason.

In this imagined debate, al-Ghazālī’s sensory experiences strengthen their argument by appealing to an analogy with dreaming. When dreaming, we believe with certainty that what we’re dreaming is true. But, we wake up and realize those dream beliefs are untrue. So, by analogy, if we were to have a third type of experience—one that was neither a dreaming nor waking experience, we could doubt the beliefs we normally have while waking. Having this third type of experience would be similar to waking from a dream: we would be “waking up” to a higher reality.

Much later in Deliverance (¶82ff), al-Ghazālī returns to a discussion of the possibility of this third type of experience. He proposes that we all do have an ability that goes beyond reason—the ability of prophecy. Although most of us do not recognize these experiences as such, Sufis—Islamic mystics[5]—as well as the prophets, are “masters of [these] states” (¶83) through their devotional practices. Al-Ghazālī calls such experiences “fruitional experiences,” and through them we have an intimate relationship with Allah (God). Given the perfections of Allah, especially that He is all-knowing and good, one’s fruitional experiences of Allah provide certainty to many of our sensory and rational beliefs. In other words, according to al-Ghazālī, one only knows once one has fruitional experiences of Allah.

Even if one doesn’t accept the existence of Allah or fruitional experience, one can still raise doubts about the certainty we associate with reason and self-evident truths because we can entertain the possibility of a higher ability through the analogy that al-Ghazālī’s personified senses offer the reader.

3. Conclusion

At the start of Deliverance From Error, al-Ghazālī raises a number of skeptical concerns about the nature of knowledge to cast doubt on beliefs that, at first glance, appear to be certain. In the rest of the letter, al-Ghazālī recounts his study of various disciplines—rational theology (kalām) (¶s 18–24), Aristotelian philosophy (¶s 25–60), Ismāʿīlism (¶s 61–79), and Sufism (¶s 80–101). None of these disciplines, except for Sufism, enable al-Ghazālī to overcome the doubts he raised with his Dream Argument.


[1] For an introduction version of Descartes’ Meditations see Descartes’ Meditations 1-3 and Descartes’ Meditations 4-6 by Marc Bobro. The Meditations are the source of the well-known phrase, “I think, therefore I am.” For an explanation of the significance of that insight, see Descartes’ “I think, therefore I am by Charles Miceli.

[2] Descartes is thereby associated with skepticism, the view that we know very little, if anything, since—on this view of knowledge—knowledge requires certainty.

There are various forms of skepticism. An extreme form of skepticism, often called global skepticism, is the view that nobody knows anything at all. Another extreme form of skepticism is external world skepticism: this is the view that no beliefs about the external world, such as sensory-based beliefs about what exists in the external world beyond our own thoughts, are knowledge: see Andrew Chapman’s External World Skepticism. More limited skepticisms claim that we lack knowledge in certain areas, e.g., that there is no scientific knowledge, or that there is no religious knowledge and so no religious beliefs are known, or that there is no moral knowledge and so nobody ever knows whether actions are right or wrong.

Many forms of skepticism, however, are common and justified: e.g., skepticism about beliefs gained from well-known sources of propaganda or astrology or mere wishful thinking: we don’t gain knowledge from any of those sources. For an explanation of a common philosophical theory of what knowledge is, see Andrew Chapman’s The Gettier Problem & the Definition of Knowledge.

[3] References to this text include paragraph numbers that follow the translator’s numbering.

[4] “The thirst for grasping the real meaning of things was indeed my habit and wont from my early years and in the prime of my life. It was an instinctive, natural disposition placed in my makeup by God Most High, not something due to my own choosing and contriving. As a result, the fetters of servile conformism fell away from me, and inherited beliefs lost their hold on me, when I was still quite young.” (¶6)

[5] Broadly construed, Sufism is a mystical and ascetic tradition within Islam. Although it is not a sect of Islam (e.g., Sunni or Shia), historically most Sufis have been Sunni. The general aim of the tradition seeks a purification of one’s heart to understand and form a direct relationship with Allah. Within the Sufi tradition, adherents may engage in numerous practices, including fasting, breathing and mantra meditation, recitation of the Qu’rān, and other acts of piety, for purifying one’s self of selfish desires and ego so to better experience Allah.


al-Ghazālī, Abū Ḥāmid. Al-Ghazali’s Path To Sufism: His Deliverance from Error, translated by Richard McCarthy, S.J.. Fons Vitae, 2000 (Originally written circa 1110 CE).

Descartes, René. Meditations on First Philosophy, translated by Jonathan Bennett, 2017 (Originally published 1641 CE).

Related Essays 

Descartes’ Meditations 1-3 by Marc Bobro

Descartes’ Meditations 4-6 by Marc Bobro

Descartes’ “I think, therefore I am” by Charles Miceli

External World Skepticism by Andrew Chapman

Moore’s Proof of an External World: Responding to External World Skepticism by Chris Ranalli

The Gettier Problem and the Definition of Knowledge by Andrew Chapman

Epistemology, or Theory of Knowledge by Thomas Metcalf

Epistemic Justification: What is Rational Belief? by Todd R. Long

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About the Author

John Ramsey is currently a freelance academic editor and works with multilingual and early career academics. His philosophical interests are in early Chinese philosophy, Buddhist philosophy, and Pragmatism. His academic work has appeared in Philosophy East and WestThe Journal of Chinese Philosophy, and Asian Philosophy. 

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