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Rene Descartes: Meditations on First Philosophy

Nikki Alberta has a Master of Arts in Philosophy from the University of Alberta. She is a freelance article writer, novelist and blogger.


Rene Descarte (31 March 1596 – 11 February 1650) was a French rationalist philosopher opposed to empiricism. Meditations on First Philosophy was written in 1641 and has the subtitle 'In which the existence of God and the immortality of the soul are demonstrated'. The work is composed of six meditations that explore his metaphysical system. Using the method of radical doubt he hopes to uncover that which cannot be doubted to use as a foundation. He states “I set forth the reasons for which we may, generally speaking, doubt all things especially about material things.”


Meditation I: Concerning Those Things That Can Be Called into Doubt

He begins this process by eliminating all things that can be doubted in order to find that which cannot be denied to establish a foundation. “I must once and for all seriously undertake to rid myself of all the opinions which I had formerly accepted and commence to build anew from the foundation.” (165). This is referred to a methodological doubt where everything is to be doubted even that which is almost certain. If it can be doubted, then it should be.

The senses are known deceivers and if they have deceived us before then they should be doubted. We know for example that the senses bring in a great deal of sense data that the brain then interprets as needed. Information can be excluded and skewed depending on situations and perspective. This is why we can be thrown by optical illusions that appear to be what they are not. The brain’s process of interpretation means that it can see patterns or fill in gaps when there is not sufficient information. Because of this ability we can see patterns were there are none, we can see faces in random designs and bunny rabbits in clouds. Since the brain is interpreting all that data if something is wrong with the brain it can lead to wildly skewed interpretations, delusions and hallucinations. It can be agreed that while a great deal of what we understand through our senses is accurate some of it is not. I get migraine auras that cause me to see ‘visual snow’ or a thousand dancing pinpricks of light cascading through my vision. I have heard someone with a similar problem believe that visual snow was something mystical outside of his brain. While I see the same phenomena, I doubt that. I also get Alice in Wonderland Syndrome from migraines were my perception of my body is skewed, objects appear to be the wrong size, distances too long and objects can warp and shift. Therefore, I know seeing is not believing and sense data is not always interpreted to match reality. In fact, since what we know of reality is interlocked with our perceptions we know we cannot be sure of what is really real. So Rene Descartes sets aside existence outside of the mind because aspects of it can be doubted and our we can be deceived.

He uses the example of dreaming versus reality to express this. "I am in the habit of sleeping, and in my dreams representing to myself the same thing or even less probable things... 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.' (Descartes p.135-6). While everything we dream about is not referring to reality at all, it feels just as real while we are dreaming than existence while awake. We cannot know reality through our senses when our senses may tell us what appears to be there rather than the truth. So we must doubt our senses and because at any moment we could be dreaming, we must doubt the external world.

Surely some things cannot be doubted. With mathematics, whether we are dreaming or not, 2 +3 = 5. For "whether I am awake or asleep, two and three together always form five, and the square can never have more than four sides, and it does not seem possible that truths so clear and apparent can be suspected of any falsity." (Descartes p.137) This is a priori and thus known independent from observation. Yet what if we are deceived in this such that every time we believe 2 + 3= 5 we are wrong? Descartes employs the idea of an evil genius to show that even this knowledge must be doubted.

“I shall suppose, not that God who is supremely good and the foundation of truth, but some evil genius not less powerful than deceitful, has employed his whole energies in deceiving me; I shall consider that the heavens, the earth, colors, figures, sound, and all other external things are nought but the illusions and dreams of this evil genius has availed himself in order to lay traps for my credulity.” (Descartes, p.138).

Well, if we employ his radical doubt to this extent, indeed there does not seem to be anything that cannot be doubted.

Meditation II: Of the nature of the human mind

Since an evil genius may be planting false knowledge in us what cannot be doubted? We may be delusional or dreaming as well and we would not know it. The whole external world can be doubted.

He realizes even if we are being deceived we cannot doubt our own existence. “I am, I exist, is necessarily true each time that I pronounce it, or that I mentally conceive of it.” (171). He states thought is an attribute that belongs to us and cannot be separated from us. We are ‘a thing which thinks’; we doubt, conceive, understand, affirm, deny, will, refuse, imagine and feel. In his representational theory there is a separation between ideas and external things. Indeed if we know the brain takes in sense data and then adds in the interpretation there is indeed a separation.

He uses the example of wax; we know its color, its shape and size, every characteristic needed to identify it as wax, but when it is heated, its color is altered, it loses its shape and its size increases. All the characteristics and sense data changes and yet we still know it to be wax. What he wants to note is that “its perceptions is neither an act of vision, nor of touch, nor of imagination, and has never been such although it may have appeared for merely to be so, but an intuition of the mind.” (Descartes, p. 145) There being a distinction between ordinary perceptions and judgements; “it is certain that although some error may still be found in my judgements, I can nevertheless not perceive it thus without a human mind.” (Descartes, p. 146). It is not the ordinary perceptions, or sense data that is important but rather the judgements and understanding we impose on them.

This then is our concrete foundation but how do we get back our certainty of the external world and our bodies?

Meditations III: Of God's existence

This is our solid foundation, but how do we get the external world or our body back into what can be known? Descartes states we must be rid of the evil genius. The only way to be rid of this possibility is to prove the existence of God, since God would not deceive us. If “the objective reality of any one of my ideas is of such a nature as clearly to make me recognize that it is not in me either formally or eminently, and that consequently I cannot myself be the cause of it, it follows of necessity that I am not alone in the world, but that there is another being which exists, or which is the cause of this idea.” (Descartes, p. 154).

God is understood by Descartes to be “a substance that is infinite, independent, all-knowing, all-powerful, and by which I myself and everything else, if anything else does exist, have been created.” (Descartes, p. 156). Such concepts of the infinite, for us finite beings, do not come from our minds alone and therefore are attributed to something outside of the mind. God gives is innate ideas of his nature, opposed to factitious, and adventitious ideas.

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Descartes' proof for the existence of God goes thus:

1) A being who doubts is an imperfect being.

2) I doubt, therefore I am an imperfect being.

3) Yet I can only be aware that I am imperfect by having the concept of perfection. Therefore, I do have the concept of perfection.

4) I could not have gained the concept for perfection from something that is imperfect. Therefore, the concept is not derived from my own reasoning. “For how would it be possible that I should know that I doubt and desire, and that I am not quite perfect, unless I had within me some idea of a Being more perfect than myself.” (Descartes, p. 156).

5) Therefore my concept of perfection must come from something perfect. "I do not easily recollect the reason why the idea that I possess of a being more perfect that I, must necessarily have been placed in me by a being which is more perfect." (Descartes p.158)

6) Only God is actually perfect, so I derive my concept of perfection from him, and therefore, he exists.

Descartes follows this with the fact that God is not a deceiver because fraud and deception are a defect, which a perfect being would not have.

Whether or not we agree with his proof for God’s existence, it is necessary for Descartes' argument, for by proving God’s existence we banish the possibility of an evil genius. Since the possibility of an evil genius was the only reason to doubt mathematics, mathematics is now valid. Since our innate ideas likewise were not planted within us by a malevolent being, they have the possibility of being valid. We also know that the external world, and our bodies, actually exist because God would not deceive us. However, our senses and perceptions of that reality can be faulty and imperfect, thus we must rely on science and mathematics to verify the external world. Since it is the mind or soul that is fundamental, Descartes is a dualist, believing that the mind is separate from the body.

Meditation V: Of God, that he exists

We are on the path to expanding known items to include material objects but on the way Descartes pauses to the ideas of these external objects.

Descartes makes a separation between external objects that are clear and distinct to those that are obscure and confused. Ideas that are clear are extension, duration and movement. Geometry cannot be combined in such a way as to make them false. We cannot re-arrange a triangle to be formed from angles that add up to the sum of 189 degrees rather than 180 degrees, according to Descartes understanding, which makes some truths to have an essence to themselves. “Suppose, for example, that I have a mental image of a triangle. While it may be that no figure of this sort does exist or ever has existed outside my thought, the figure has a fixed nature (essence or form), immutable and eternal, which hasn't been produced by me and isn't dependent of my mind.” (Descartes, p. 164).

Likewise for Descartes the idea of God is certain. While we can imagine external objects we can also know they do not exist, whereas God cannot be understood as not having existence. Quite simply put, God is an infinitely perfect being, perfection includes the idea of existence and therefore God exists. Truths are only possible with the clear knowledge of God’s existence: “Thus I plainly see that the certainty and truth of all my knowledge derives from one thing: my thought of the true God. Before I knew Him, I couldn't know anything else perfectly. But now I can plainly and certainly know innumerable things, not only about God and other mental beings, but also about the nature of physical objects, insofar as it is the subject-matter of pure mathematics.” (Descartes, p. 164).

Meditation VI: Of the existence of material things

External objects can exist because God made them: “Insofar as they are the subject of pure mathematics, I now know at least that they can exist, because I grasp them clearly and distinctly. For God can undoubtedly make whatever I can grasp in this way, and I never judge that something is impossible for Him to make unless there would be a contradiction in my grasping the thing distinctly.” (Descartes, Meditation VI). Therefore we have the possibility for the existence of the external world, unless you are an atheist, in which case, you are out of luck. Basically according to Descartes the only way to know the external world exists is because “God is no deceiver, it is very manifest that He does not communicate to me these ideas immediately and by Himself, nor by the intervention of some other creature in which their reality is not formally, but only eminently, contained.” (Descartes, p. 182) and “I do not see how He could be defended from the accusation of deceit if these ideas were produced by causes other than corporeal objects.” (Descartes, p. 182).

He draws the distinction between imagination and understanding.

When I have a mental image of a triangle, for example, I don't just understand that it is a figure bounded by three lines; I also "look at" the lines as though they were present to my mind's eye. And this is what I call having a mental image. When I want to think of chiliagon, I understand that it is a figure with a thousand sides as well as I understand that a triangle is a figure with three, but I can't imagine its sides or "look" at them as though they were present... Thus I observe that a special effort of mind is necessary to the act of imagination, which is not required to conceiving or understanding; and this special exertion of mind clearly shows the difference between imagination and pure intellection.” (Descartes, p.182).

Descartes goes on to illustrate proofs the mind is distinct from the body. It is possible for God to create anything that we can distinctly perceive and if he creates something to be independent of each other then they are distinct from each other. We know from earlier we can understand ourselves as a thinking thing, without considering the existence of the body therefore God can create a thinking thing independent from material substance. We understand, as well, our bodies to be an extended thing, that does not require a mind, so God, likewise, can create a body independent of a mind. (I think I have met people like that) We therefore can say a mental substance is separate from a material substance and we can exist without a body. However, one would think if there is a God then he could also create a mind and a body combined that are not distinct and cannot exist separately… because he is god and he can do that if he wants to.

In regards to proving the reality of external things, while our senses can deceive us, we have a strong belief in the reality of the external world because of our senses. God, being that he would not deceive us with all this random and false sense data, must have designed us with this nature. If the external world does not exist then God is in fact a deceiver, but as stated previously, that is not very god-like. Therefore, material things do exist.

Meditation 4-6


I must say what I find most intriguing about these meditations is the idea of radical doubt. Indeed, I am aware of several ways our brain falsely interprets sense data that can lead us to doubt the accuracy in which we interpret the world. Such that there is always a level of interpretation when it comes to our being in the world and science would be a way to try to validate reality ourside of our perceptions. I like that we end up reducing everything to the 'I' because really when it comes down to it our reality is dependant on the core of 'I exist' and the I in relation to the external world. Using radical doubt and ending up with only this 'thinking thing' intrigues me but building on that foundation is quite a bit tricky.

However, I have never found any proofs for the existence of a god to be particularly overwhelming enough to convert me from my wavering Agnostic stance so depending on god for any theory does not work for me. Without that firm and clear belief it does not follow that we have any guarentee there is in fact an external world and even if we rather believe there is we cannot be confident of our interpretation of it. Aside from the possibility of an evil genius deceiving me I rather believe science is a way to validate the external world, as much as it can be, outside my own perceptions.

Nevertheless I have a fondness for Descartes and his radical doubt. Using radical doubt I might say since I can doubt the existence of God, I must doubt it. I might believe concepts like 'nothing', 'infinite' and 'perfect' are concepts created by the mind from our capacity to extrapolate but do not actually exist in reality.


Descartes, Rene Meditations on First Philosophy

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