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Descartes, Doubt and Divine Deception

Paul Sperring


In issue 15 of the RJP I set out Descartes' attempted proof of the existence of the material world. It was shown how Descartes' proof rested on earlier arguments in the Meditations (for instance, concerning clear and distinct ideas, and God's existence), and that Meditation VI provided Descartes, at least to his own satisfaction, with a series of ripostes to the major sceptical worries introduced right at the outset of the book.[1]

In this paper I should like to say rather more about the central plank of his strategy, the warrant for belief in the external world provided by a benevolent God. If Descartes is to successfully appeal to the divine guarantor in the attempt to show that things are, pretty much, as they appear (at least, that there is an external world of mind-independent objects of some form or another), then any reasons to suppose that God could or would deceive us would let the demonic sceptical arguments come rushing back in. What, after all, could be more likely to throw us into doubt than the possibility that a supremely perfect being was pulling all of the sceptical strings?

Thomas Hobbes, in the Third Set of Objections to the Meditations, had wondered if deception could be consistent with divine benevolence - parents or kindly doctors can shield children or patients from unpleasant truths for benevolent reasons.[2] All one would need to show is that Descartes' God could sometimes directly deceive us for our own good, and then this would render Him useless as a guarantor for the belief that the material world exists independently of our minds. Descartes realised this, and in his rather brisk reply to Hobbes admitted that no sort of deception at all can be laid at the divine feet if the proof of the material world is to be sound. It is undeniable, however, that we do make mistakes, but that these mistakes cannot be directly attributable to God is something that Descartes must show.

The strategy he adopts is to select the hardests sort of case for the theist - those deceptions that arise as a result of the workings of nature - and to explain those away. This removes the sort of counter-example that would support Hobbes' contention that it needn't be universally true that divine perfection and divine deception are not compossible. However, there is more at stake here than the defence of the proof of the material world. It looks as if we can construct a powerful anti-theistic argument with three claims Descartes makes.[3] First, that deception is simply logically inconsistent with God's supreme perfection. Second, that there is a natural propensity to make mistakes. Third, that nature is thought to be nothing other than God himself.[4]

Descartes' Theodicy

The question that Descartes takes on in Meditation VI, to shore up his proof of the existence of the material world by eliminating the possibility of divine deception, is:

How is it that we are naturally deceived if God is the creator of everything?

Descartes sets up the problem in a way familiar to anyone who has encountered the problem of evil. There the theist is presented with a challenge to explain how three propositions could be held to be true conjointly, viz. a) there is an omnipotent God; b) there is an omnibenevolent God; and c) there is evil and suffering in the world. Theodicies were constructed by theists to reconcile the three commitments and show that, after all, God could be considered just in the face of misery and suffering. However, Descartes' concern is not with evil done or evil suffered, but with deception (a kind of epistemological spin on the classic problem). So what doesn't fit for the theist?

Take the following propositions:

(i) God is supremely perfect.
(ii) God made all that there is.
(iii) I am naturally led to be deceived.

If (i) is true then it seems that (ii) and (iii) can't both be true since this would seem to suggest that God either made a faulty thing, or wasn't responsible for something that occurred in the universe. So, if we accept the truth of both (ii) and (iii) then (i) will have to go. But no theist is going to want to give up (i).

What if we deny (iii) - after all, if (i) and (ii) were both true this would seem to rule out (iii) a priori. Well, it just seems to fly in the face of observed facts to consider (iii) false (somewhat akin to the Christian Scientist's treatment of the classical problem by flatly denying that there is any such thing as evil and suffering). So what observed facts must we consider as confirming (iii)? Descartes gives two examples:

Phantom Limbs - when a person has had a limb amputated they continue to feel sensations (itches, pains, etc) in the missing fingers or toes.[5] So the body here is telling us we need to scratch our toe, but this cannot be the case, since our toe may well have been incinerated after the operation to remove it, and so the toe itself cannot be in any state at all.

Dropsy - this is an illness which has the symptoms of causing extreme dryness in the throat of the sufferer, and therefore suggestive of the need to take on fluid.[6] However, dropsy is a condition that can result in death if one takes in fluid. So once again the body appears to be telling us something ('you need to drink!'), which is not just false, but potentially fatal.

Now an easy answer to this puzzle (which Descartes considers and then rejects) is to suggest that these are examples of defective bodies (which have departed from their nature) and are therefore no challenge to the theist since a normal body would not be subject to deception naturally. Descartes is right to reject such a move, since, he says: 'A sick man is no less one of God's creatures than a healthy one.' (CSM II, 58)

Descartes' proposed solution to the puzzle is twofold. The first stage explains why and how the 'deception' arises. The second stage then explains how that 'deception' can be avoided, and therefore shifts the blame from God to us (again, familiar from many of the attempts to get God off the hook in the responses to the classical problem of evil).

Stage 1: What Is The Source Of Deception?

According to Cartesian Dualism although the mind and body are distinct substances they are united to form one whole. The mind interacts with the body at one point only (the pineal gland, found in the centre of the brain), whereas the information it receives arises from diverse parts of the body. This follows from their natures - since the body as extended must by that fact be divisible into parts, and the mind as non-extended cannot be divisible into parts (it is indivisible).[7]

Now, the mind is only in a position to accept information as it is somehow conveyed by the activity of the pineal gland.[8] So if different stimulations in different parts of the body cause the same activity with respect to the pineal gland, then it must appear to the mind as if the same parts are affected and in the same way.

Take the phantom limb case. Imagine a nerve stretching from the pineal gland to the fingertip, and that nerve has four points on it ABCD (A being the point nearest the gland, D the furthest). Now, once a person has had an amputation their nerve still has points A-C. If point C is stimulated in such a way that it would have been stimulated were point D still in existence then the information transmitted up the nerve could be presented to the mind as if it arose from D.  [Skip box]

In Descartes' The Treatise on Man (1664) he says of the normal functioning of the nervous system:

'If the fire A is close to the foot B, the small parts of this fire, which, as you know, move very quickly, have the force to move the part of the skin of the foot that they touch, and by this means pull the small thread C, which you can see is attached, simultaneously opening the entrance of the pore d, e, where this small thread ends...the entrance of the pore or small passage d, e, being thus opened, the animal spirits in the concavity F enter the thread and are carried by it to the muscles that are used to withdraw the foot from the fire.'[9]

Imagine a long piece of wire with a bell attached at one end and a pull cord at the other. Now suppose that I pull the cord in one room and the bell rings in another. If someone is in the room with the bell, hearing it ring, they will assume that the cord is being pulled from the room where the wire ends. However, it would be possible to tug the wire from any point between the cord and the bell, say from just outside the room where the bell is. The person in the room, accustomed to being summoned to the far-off room where the cord is, would assume that that is where the motion arose from (this sort of practical joke would amuse waggish servants, getting the poor butler or footman to trudge off to some distant corner of an old stately home in response to what they thought was the summons from the master bedroom, or library, when in fact the wire was pulled from just outside the kitchen). The soul is in the position of the butler or footman here. It takes the information it receives at face value, since it cannot be out there in the body/stately home to verify things.

Now there is nothing chaotic about this arrangement. We would expect nothing else of the behaviour of wires and nerves. And, it is a good thing that our nerves behave in such an ordered and systematic fashion - after all if our actual foot is in the fire, then it's a good thing that our mind is alerted to the fact, and that we don't instead get a misleading tickling sensation in our ears.

Stage 2: No Deception

Since our body tells us things more often than not that are true and the so-called deceptions arise in a systematic and explicable fashion then we do not really have anything to worry about here.

Also, we have at our disposal certain God-given faculties for avoiding deception. If I use all of my senses in combination, as well as my memory and intellect, then I wouldn't be deceived in the first place. Take the phantom limb case. If I get an itching feeling in my finger I need only look at the space below my elbow where my hand used to be, or perhaps try to touch it with my other hand, or maybe tap the non-existent finger on the table to see if it makes a sound, and so on, to tell me that I have no finger, and therefore no itch in my finger. Further, I can call upon my memory. I recall, very vividly, the operation to have my arm amputated. And finally, deploying my intellect, if the above observations have been made, it doesn't take a Sherlock Holmes to deduce that there is no finger, and so no itch (we can run the same sort of story with the dropsy case). Of course, if we have everything we need to avoid deception but rashly judge things to be the way they are on first appearance, then God is hardly to be blamed.

To adapt slightly one of Descartes' other examples, if I place a candle flame very close to my right eye I might, at first, get an idea of it as a very bright, hot, large thing.[10] When I shut my right eye and gaze at the sun with my left through a light mist I might get an idea of it as a dim, cool and tiny thing. I am immediately confronted with two ideas which, if I were not to carefully deploy my intellect, I could compare and suppose the one (candle flame) to be actually hotter and brighter than the other (sun). In Meditation IV Descartes had explained that human error arose from allowing the will to be exercised before the intellect has had a chance to get the details in order (we judge X to be the case, that is, we use our unbounded free will to choose to consider X true, before we have fully understood what we are dealing with). Now, no-one would suppose, would they, that God should have fixed nature in such a way that we should immediately grasp the true nature of the sun: that it is a huge sphere of ionized gas that radiates energy through thermonuclear fusion processes at its core. So, having set things up in the way that He has, God has seen to it that we are best able to use our faculties to make true judgements (the sun is a long way away but very hot, the flame is near but comparatively not very hot).

So, to return to our supposedly inconsistent triad:

(i) God is supremely perfect.
(ii) God made all that there is.
(iii) I am naturally led to be deceived.

We can qualify (iii) in a way that is harmless, and consistent with (i) and (ii). We are deceived not directly by nature but by ignoring our natural capacity for truth detection.


Has Descartes successfully dealt with the cases of natural deception?

It seems right to claim that we have, under normal circumstances, with respect to medium sized dry goods, pretty much what we need to avoid falling into gross error concerning the world around us (such as thinking one has hands when one doesn't, or that the sun's diameter is smaller than that of a ten pence piece). We could go further, and suggest that, as we have discovered more and more about the world, that our God-given faculties have been tremendously successful in digging out the truth. We can only blame ourselves for our past mistakes where we have assented to claims we have no right to make. Perhaps we can say that it is at least possible that all cases of so called natural deception are in fact cases of mistakes made by the intellect that could have been avoided by more patient and careful reflection. In which case, Descartes' argument comes out as plausible if we consider the puzzle as a merely logical one - can the propositions (i)-(iii) all be true?

But how does it come out if we wonder if all of the propositions are true. That is, what is the likelihood of a supremely perfect being leaving so much up to us? Given the fact that we are so error prone, and so frail as to go wrong so often (the sick man is not simply no less one of God's creatures than the healthy man, he is also by no means a rarity), is it really likely that Descartes' God created the world?

In short, we have the 'logical' and the 'evidential' problems of deception before us here. Descartes has perhaps shown, at best, that nothing in nature necessitates the judgment that God deceives us. That it is logically possible that all cases of deception that arise from the way the world is are based on things not fully noticed by us, but that would have been noticed if we were rather more attentive. Given the way the world is fixed, however, it seems unreasonable to suppose that we could always avoid error (consider the poor benighted caveman who has an overwhelming hunger and eats a type of grub that is, to his eyes, indistinguishable from its edible cousin, but that is fatally poisonous).

And so, in conclusion, we have an intellectually polished solution to the puzzle, but one that leaves us unconvinced - just as, one might say, we have in the classical problem of evil.

Paul Sperring
Brighton College


[1]  All references to Descartes' text in this essay come from The Philosophical Writings of Descartes, translated by Cottingham, Stoothoff and Murdoch (CSM Vol. no, Page no.), which is translated from the Oeuvres de Descartes, edited by Adam and Tannery (AT Vol. no, Page no.)).  [back] 

[2]  CSM II, 136; AT VII, 195  [back] 

[3]  Grist perhaps to the rumour mill that Descartes was not really a theist - that the God proofs were a political expedience designed to get the Church off his back and to allow him to do his science unmolested. Descartes, this sort of view runs, was smart enough to realise the consequences of his claims, and also too smart to really think that there are no real examples of imperfection in nature, thus he would have privately come to the conclusion that there couldn't be a supremely perfect being. Revisionist readings of Descartes no doubt have their place, but this one seems just a little bit too 'out there' to be taken seriously - after all, in private correspondence or unpublished notes, there isn't even the merest hint of agnosticism, let alone full blown atheism.  [back] 

[4]  See CSM II, 56; AT VII, 80: 'For if nature is considered in its general aspect, then I understand by the term nothing other than God himself, or the ordered system of things established by God.'  [back] 

[5]  Some links to information on phantom limbs:

Professor Vilayanur Ramachandran's 2003 Reith lecture: http://www.bbc.co.uk/radio4/reith2003/lecture1.shtml
Wikipedia entry: http://en.wikipedia.org/wiki/Phantom_limb
Wellcome Institute: http://www.wellcome.ac.uk/en/pain/microsite/medicine2.html  [back] 

[6]  'Dropsy' was a term used to refer to the swelling of soft tissues due to the accumulation of excess water. The modern-day term for such a swelling is an oedema. (See http://www.medterms.com/script/main/art.asp?articlekey=13311)  [back] 

[7]  For more on this see CSM II, 59; AT VII, 85-86  [back] 

[8]  For Descartes on the pineal gland, see his Passions of the Soul, Articles 31-36. For more detail, see this excellent Stanford Encyclopaedia of Philosophy article.  [back] 

[9]  The Treatise on Man was first published in 1664 but dates from between 1629-1633.  [back] 

[10]  CSM II, 57; AT VII, 82  [back]