Part IV is perhaps the most important part of René Descartes’ Discourse on the Method. This part of the Discourse contains a description of the results of Descartes’ meditations following the method that had been previously established by him. In contrast, earlier when Descartes was doubtful, he had taken upon himself to act conclusively and definitively. Now he acts oppositely, and considers everything that may in anyway be doubtful as false. He does this to be certain that the things he holds on to are impossible to doubt. He completely gives up all sensory knowledge because the senses are prone to deception and all demonstrative reasoning because the reasoning demonstrated by human beings is prone to errors. Instead, Descartes’ imagines that it is dreams that brought everything that is present inside his mind and that all those things are nothing but illusions. As absurd as Descartes’ imagination seems to be, the surprising aspect of Part IV of the Discourse is that it takes an unexpected turn from what Descartes’ was initially focused on proving.
Initially, the focus of the Fourth Part of Descartes’ Discourse seems to be proving his own existence. That is why he perceives that even if doubts everything that his in his mind, in order to doubt he must exist. He perceives that if he doubts his senses it means that he is thinking and since he is thinking, it confirms that he exists. This is how Descartes ends up asserting his famous assumption, “I am thinking, therefore I exist” (Bennett, 2007, p. 15), and decides to build upon this foundation, which he assumes is impossible to doubt. Since Descartes’ exclusively basis his knowledge of his existence on his thinking, he reaches the conclusion that he is a substance “whose whole essence or nature is simply to think” (Bennett, 2007, p. 15), and that his soul is absolutely different and separate from his body, and knowing the soul is easier than knowing the body. Up till this point it remains somewhat apparent that Descartes’ is trying to prove his existence, however, the direction of his argument turns elsewhere beyond this.
Descartes’ notes that although his assumption that he is thinking, therefore he exists is not really persuasive, but he seems to be distinctly certain that it is essentially true. Thus, he proposes that truth can only be guaranteed only by adopting perceptions that seem to be essentially true, without the shadow of the doubt. Although Descartes agrees that thoughts of external objects, such as the earth, light, the sky, etc. could all be a deception or a fallacy, he claims that this is not the case with God. It is at this point that Descartes surprises the reader since the focus of his Discourse suddenly begins shifting. He adds that those objects are imperfect and an imperfect mind could easily invent thoughts about them. However, it is not really conceivable that the notion of a perfect God was invented by Descartes’s imperfect mind because that would mean that the existence of God, a perfect being, is dependent on an imperfect being. The surprise ending occurs when Descartes reaches the conclusion that God is a perfect mind, and that it is because of his perfections that other bodies have perfections in themselves.
Even after surprising the reader and shifting the direction of his Discourse to prove the existence of God instead of his own existence, Descartes makes use of geometry to arrive at another piece of evidence. He notes that how certain geometers are in proving the facts that when all the angles in a triangle are added up they are always equal to 180 degrees. He states that even though this is believed to be a fact, there is nothing assuring him a triangle actually exists in the world. He then proceeds by claiming that it can be believed within certainty that when adding up the angles in a triangle the answer is always equal to 180 degrees even though there is nothing assuring that a triangle really exists, similarly, God’s existence is most definitely certain even if there is no assurance that God exists. In other words, compares God’s existence to geometric proof to reach the conclusion that both are equally certain. Descartes exclaims that people solely rely on their imagination and senses so they are not able to comprehend these proofs. His surprise conclusion is that we can only perceive God’s existence by reason, and not by imagination and senses.
The truth is that Descartes’ argument goes into a complete surprising circle when he claims that the truth of apparent and evident perceptions is confirmed by God. This means that the implication of his notion is that apparent and evident perceptions can only be true if God exists. Descartes may have claimed that all truth, including apparent and evident perceptions, are dependent on God, but he has yet to conclusively prove that God exists. Moreover, not only are Descartes’ “proof” not really original, they are also not quite satisfying. Descartes’ notions about certainty and the nature of the mind were certainly groundbreaking; however, apparently he has borrowed his evidence to prove God’s existence from the medieval scholastic tradition. Descartes’ first proof that since God is a perfect idea, therefore, only something as perfect as that idea itself can create it is quite questionable since it is based on notions of causation. Descartes is second proof that just like a triangle has the property that all of its angles add up to 180 degrees, similarly, God has the property of existence was already proven inconclusive by Kant (McCormick, 2005). Therefore, Descartes fails to convince me with his surprise ending.
McCormick, M. (2005, Jun 30). Kant, immanuel: Metaphysics. Retrieved from http://www.iep.utm.edu/kantmeta/
Bennett, J. (2007, Nov). Discourse on the method of rightly conducting one’s reason and seeking truth in the sciences. Retrieved from http://www.earlymoderntexts.com/pdf/descdisc.pdf