In this essay I will be critically assessing Descartes’ method of doubt and attempting to come to a conclusion on how successful it is as a method of acquiring knowledge. I will first lay out what his method of doubt is and the potential problems with it, what the conclusions are and why and why not I agree with them. I will then be attempting to come to my own conclusion of how useful his method is in the form that he used it, and also in the form that it is now used.

So, to begin Descartes’ method of doubt is a systematic method of reducing all that we think we know to true or false statements. If it can be doubted, it must be (To Descartes) relegated to the default status of untrue. He used this in order to find what was indubitable, with intention to use those facts as a foundation for all knowledge. It is a method of reduction to begin again by making sure you only have facts to work upon, as if you do not you’re potentially building on false knowledge and thus making false conclusions, building and building upon falsehoods. Which has the horrifying conclusion that everything can and will fall apart when questioned.

He began this process with a method of throwing away every piece of information that he could doubt. He used a dream argument (1) to prove that all that he thinks he knows could be from a dream state, as dreaming for himself was impossible to separate from reality, as what we think of as dreams are only revealed to us when we wake. If we never wake, we would never know, thus life and reality could be an unwaking dream. Leaving the idea of reality in a limbo of not knowing and being unable to conclude if it is true or not.

He then brought in the demon argument, (2) which argued that all of our senses could be mistaken by the fault of some evil demon, making us doubt and giving our senses false information. Seeming as he had already made the dream argument, other than setting himself up for bringing in God to refute the evil demon and making mathematics dubitable, there seems no point to his demon argument when you compare it to the dream one.

Such arguments led Descartes to one and only one solid undoubtable fact: “I think, therefore I am.” Now this claim can be questioned on the level of what is the I and what does it mean to think, but the important thing here is that the essential existence is self-evident and cannot be refuted, no matter what the existence is or how it manifests itself, the existence exists. It is a self proving claim. Descartes tried to bring us from the inner existence fact to the outer existence of everything else by using God. (3) God is known to be perfect, therefore must exist and cannot do Evil, as doing evil would be an imperfection.

To Descartes this proved that God was no evil demon, and no evil demon could be doing such things; as God would intervene with his creation and wouldn’t allow us to be deceived. As is self evident, Descartes’ God argument is easily doubted by the mere fact that God is not self evident and could not the demon be God? Why does god have to be perfect? And why can the devil not exist without god? Which leaves us with the clear conclusion that both the God and Demon argument are the same argument, but reverses of each other. Doubtable and unreliable, Descartes proof of the outer world and our senses being indubitable is doubtable.

As can be seen concerning Descartes’ method of doubt, there are several problems with it. First off “I think, therefore I am”, the statement can be put into doubt. As Thomas Hobbes pointed out:

“It is not through some further consciousness (Cogitationem) that it is inferred I am conscious (Me cogitare); a man may be conscious of having been conscious, and this consciousness is simply memory, but it is quite impossible to be conscious that one is conscious, or know that one knows. For otherwise there would be an unending question: how do you know that you know that you know that you know-?” (4)

Although this does not bring into question the actual existence of the self (Which Thomas Hobbes admitted), it does leave his statement of the cogito somewhat useless. Whether true or not, known or not, it says nothing about the outer world and is an entirely useless foundation and fact which seems pointless and impossible to build on. The other problem is that Descartes’ method of doubt leads him to the troubling conclusion of Cartesian thinking. The idea that the body and the mind are separate but living as one, intermingled. Thus making the body a machine and the mind the real entity of self; the thinker and decider. In other words; the god of the body.

Concluding on Descartes’ method of doubt, it is a useful and interesting thought experiment that leaves us with a fresh perspective on everything we accept as true; his conclusions that tried to bring in the outer world were doubtable, although the existence of existence is not. In this way, the method is useful and sticks to the Aristotelian way of thinking:

“He who seeks to acquire knowledge must first know how to doubt, for intellectual doubt helps to establish the truth.” (5)

Which brings me to the question “How successful is it as a way of acquiring knowledge?” The answer is both not successful at all but all very successful when tweaked. What I mean by this is Descartes’ method is not successful because of his strict idea of what cannot be true and what it means for something to be true; That which is not doubtable. According to his method, we can only truly know that we exist and that we do not know anything but that we exist and that we do not know anything more than these two said things. Leaving us trapped within the inner world. Also the Cartesian concept stems from this idea and helps to over come it, however the Cartesian thought and ideas are highly problematic, which is not to say that it’s not true, as I and Descartes could not possibly know such a thing, but makes the potential of it being true far less likely.

To use a contemporary example in order to illustrate my point: The Cartesian idea is that the body and mind are distinct but can interact with each other; like controlling a robot, however when the body feels pain, distress or any emotional state, the body is not feeling it, the mind is. In that sense the mind is integrated within the body unlike a driver in a car, but more like someone plugged into a body which is then assimilated as a part of the self and mind. This becomes confusing when you apply it to modern examples of the body. For example a man who has lost his arm in some tragic accident and has a robotic one grafted on cannot feel or direct the arm, it is like putting a item of clothing on and it is forced to move with your movements in a mechanical fashion. However this is a problem to Cartesian thought when the robotic arm is literally grafted into the arm flesh and bone, and can individually move fingers, not by the movement and motion of the arm muscles and bone, but purely by thought. This has been done and is the cutting edge of prosthetic technology. (6)

Now the problem is not clearly apparent until you consider how could the mind assimilate a fake limb into its own thinking and make it its own. How is it that the substance of mind has spread and taken over the limb which is not a limb or anything to do with the self? Also, how is it that the body: A machine; Can accept and use such a limb as if it was natural to it via thoughts rather than muscles? To use a limb via thought alone presents a problem. I don’t have an answer to this problem unless I am to assume that the mind is physical and one and part of the body; one substance. (7)

To add further to this problem using a similar line of argument and topic. A prosthetic limb has been developed which is also integrated into the bone and flesh, but can literally feel touch. For example a patient picks up an object and feels the texture and dimensions on his/her finger tips which are not his finger tips but plastic, and is able to feel the sensation of touch due to implanted electrodes in the fake limb that lead to his flesh and bone arm. (8)

This just adds more problems for anyone who thinks that the mind and body are separate substances. But moving on, to conclude my answer “Not very useful at all.” to the question is based on the strict regulations of what Descartes accepted as true being far too impractical and that his conclusions using this method are doubtable and difficult to accept at best, leading to conclusions that are problematic with no foreseeable solutions.

Further moving on, my answer “Potentially very useful” to the question of how successful is the method of doubt as a way of acquiring knowledge actually stems from adjusting his strictness of knowledge. My agreement of its usefulness depends on loosening the strict restrictions on what it means to know.

What I mean by this is to take the advice of Saint Augustine:

“If I make a mistake, I conclude that I exist; for he who does not exist cannot make a mistake, so that the fact of having made a mistake is proof that I exist.” (9)

This, as can be seen, is the beginning principles of the Scientific method. That is to say that by testing and making mistakes we come to know what is not the case, thus leaving us with an idea of roughly what is so. As we test and gain a consensus whilst sharing all information with the public we come to know what is true, exactly because we know what is not the case. We thus come to certainties which are not perfectly certain and indubitable, but so close to indubitability that the difference between today’s acceptance of true and Descartes’ is pedantic. In this way Descartes was the start of a new method of thinking, and his place is rightly as the father of modern Science. For that reason his method of doubt is respectable and valuable in the context that it is used without being strangled by his strictness.

To conclude, Descartes’ method of doubt is a useful and interesting thought experiment, which should be applied at least once in order to broaden our view, and to recognise our current limits and past attempts to overcome them. Although his method of doubt is not used how he famously used it, it is now an extremely common occurrence to be sceptical and a valuable tool used to find out what we don’t know. In this way Descartes’ method is inversely used, we come to know by proving what is not the case. For that reason his legacy is extended and lived on by what he could not do, rather than what he did do. But the conclusions and progress we have made thanks to him are valuable beyond his own arguments and conclusions. Although he is commonly hailed as the father of modern philosophy, he is more accurately the father of modern science.

1. Contained in Descartes; Philosophical writings, First meditation; What can be called into question. (Open university set book, 1972 reprint, Nelson’s university paperback.)
2. Also contained in Descartes; Philosophical writings, First meditation; What can be called into question. (Open university set book, 1972 reprint, Nelson’s university paperback.)
3. Contained in Descartes: Philosophical writings; Meditation three; Concerning God; that he exists and Meditations five; The nature of material things: God’s existence considered again. (Open university set book, 1972 reprint, Nelson’s university paperback.)
4. Thomas Hobbes’ on Meditation II, Second objection. Contained in Descartes; Philosophical writings, p.129. (Open university set book, 1972 reprint, Nelson’s university paperback.)
5. Aristotle’s metaphysics quoted in The morning of the magicians by Louis Pauwels and Jacques Bergier, P.36 (1960 (Edition used is the 2007 reprint by Souvenir press Ltd.)
6. News report from Sweden published on Wednesday 8th October 2014, posted at:
7. Official Science journal source, published on 8th October 2014, titled Neuroprosthetics; An osseointegrated human-machine gateway for long-term sensory feedback and motor control of artificial limbas, posted on:
8. News report published on 10th October 2014 at:
9. Saint Augustine quoted in The morning of the magicians by Louis Pauwels and Jacques Bergier, P.36 (1960 (Edition used is the 2007, reprint by Souvenir press Ltd.)

 – Aristotle, Metaphysics
– Jacques Bergier and Louis Pauwels, The morning of the magicians (The edition used is the 2007 reprint of the 1960 original by Souvenir press Ltd.)
– Descartes (With mention of Thomas Hobbes), Descartes: Philosophical writings (Open university set book, 1972 reprint, Nelson’s university paperback.)


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