By Preston J. Werner1
We’re all familiar with Descartes’ famous “Dream Argument”, from the Meditations I:
It may be that although the senses sometimes deceive us concerning things which are hardly perceptible, or very far away, there are yet many others to be met with as to which we cannot reasonably have any doubt, although we recognize them by their means. For example, there is the fact that I am here, seated by the fire, attired in a dressing gown, having this paper in my hands and other similar matters. And how could I deny that these hands and this body are mine, were it not perhaps that I compare myself to certain persons, devoid of sense, whose cerebella are so troubled and clouded by the violent vapours of black bile, that they constantly assure us that they think they are kings when they are really quite poor, or that they are clothed in purple when they are really without covering, or who imagine that they have an earthenware head or are nothing but pumpkins or are made of glass. But they are mad, and I should not be any the less insane were I to follow examples so extravagant. At the same time I must remember that I am a man, and that consequently I am in the habit of sleeping, and in my dreams representing to myself the same things or sometimes even less probable things, than do those who are insane in their waking moments. How often has it happened to me that in the night I dreamt that I found myself in this particular place, that I was dressed and seated near the fire, whilst in reality I was lying undressed in bed! At this moment it does indeed seem to me that it is with eyes awake that I am looking at this paper; that this head which I move is not asleep, that it is deliberately and of set purpose that I extend my hand and perceive it; what happens in sleep does not appear so clear nor so distinct as does all this. But in thinking over this I remind myself that on many occasions I have in sleep been deceived by similar illusions, and in dwelling carefully on this reflection I see so manifestly that there are no certain indications by which we may clearly distinguish wakefulness from sleep that I am lost in astonishment. And my astonishment is such that it is almost capable of persuading me that I now dream.2
Discussion of this argument (as well, of course, of Descartes’ evil demon argument) is a staple of introductory philosophy courses. And though the skeptical tradition is widely acknowledge to go much further back than Descartes, credit for the dream argument itself is typically given to him. This credit is misplaced—or at least the situation is more complex than typically acknowledged.
500 years before Descartes, Islamic philosopher and theologian Abû Hâmid Muhammad ibn Muhammad al-Ghazâlî was writing his al-Munqidh min al-Dalal, commonly translated to Deliverance from Error. Of importance at present is the second chapter of Deliverance, “The Avenues to Sophistry and Skepticism.” After some initial discussion about the more common ways that sense perception can err3, Al-Ghazâlî gives his own dream argument:
For a brief space my soul hesitated about the answer to that objection, and sense-data reinforced their difficulty by an appeal to dreaming, saying: “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 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.4
While Al-Ghazâlî’s argument differs in important ways from Descartes’, they strike me as similar enough in their general spirit that Al-Ghazâlî deserves credit for providing the first sustained argument from the existence of dreaming to skepticism. (It’s also worth noting that Descartes’ argument isn’t obviously superior to Al-Ghazâlî’s.)
It’s unclear (as far as I can tell) whether Descartes’ had access to Deliverance from Error, so it’s difficult to say whether Al-Ghazâlî influenced Descartes or whether the two philosophers developed their dream arguments independently.5 And I should also stress that I’m certainly not the first person to notice the parallels here.6 However, given that many philosophers I’ve come across are not familiar with Al-Ghazâlî’s dream argument, and given the importance of the dream argument in introductory courses, it felt worth trying to more widely publicize: Descartes was beaten by 500 years!
1 I should stress that I am far from a historian. Those with more knowledge should feel free to correct the record on anything I’ve gotten wrong here. I stumbled across Al-Ghazali’s dream argument by luck many years ago, but was inspired to write this post after slowly coming to realize that this parallel is not as widely known as it should be.
2 Meditation I (trans. Haldane). (Available at https://selfpace.uconn.edu/class/percep/DescartesMeditations.pdf).
3 Note here too the similarity with Descartes, who also discusses more common ways that sense perception can err just prior to presenting his dream argument.
4 al-Ghazâlî (trans. McCarthy (1980)), paragraph 13.