In Meditation One, Descartes tries to find everything that can be called into doubt. Attacking the foundations of his own self-knowledge, Descartes demolishes his core principles and discredits every opinion, thought, feeling, and perception he has ever had. Everything, which Descartes considers doubtful, is thrown into a sort of limbo between true and false. He intends to discover the few things that are absolutely certain, and until then, everything is left in purgatory and will have to be judged at a later time. By the end of the Meditations, many critics believe that Descartes comes full circle and that everything he previously had doubts about is back. Between the first and sixth Meditations, the only certainties Descartes discovers are that he exists as a thinking thing and that God inherently exists as well. Because of this, seemingly everything Descartes doubted beforehand can be trusted again. The reasons, which made Descartes, question everything in the first place and the reasons he gives for calling it all back seem to be the same, but are they? It is never made explicitly clear if all of the things Descartes called into question did in fact return nor does Descartes explain if his reasons for doubt are the same reasons he restores everything.
By calling into doubt every opinion that is not completely certain, Descartes begins to undermine and limit his own experiences and knowledge. One of the first class of things Descartes questions is sensible things. Because they are external from the body and can only be perceived through the senses, these material and physical things can be deceiving. As Descartes says, “it is a mark of prudence never to place our complete trust in those who have deceived us even once” (28). Because Descartes cannot rely on what he believes he sees and feels, he also has to doubt that corporeal things exist. His own body is an agent for his senses, and their inconsistencies deceive his mind. Thus, composite things are also doubtful because they measure and study corporeal things which are physical and exist outside of the mind. By the second Meditation, Descartes has since called into question “the heavens, the air, the earth, colors, shapes, sounds, and all external things” (28).
Diving into the text, it seems like Descartes doubts material, corporeal, and composite things because anything acquired through the senses is untrustworthy. Descartes’s reason “persuades me that I should withhold my assent no less carefully from opinions that are not completely certain” (28). Sensing is a problem for Descartes not only because it can often be inconsistent but also because it is the stepping off point for other doubts to follow. In particular, the senses are responsible for the dream and reality confusion. Descartes’s reason dictates that if he finds any explanation to doubt his opinion then he has to mistrust it. How many times has a dreamer been duped by his sensations? Descartes says “that there are no definite signs by which to distinguish being awake from being asleep” (28). It appears then that sensation is the initial reason that everything was called into question.
In Meditation Six, Descartes has since established his identity as a thinking thing, God’s existence, and the credibility of pure mathematics. With respect to material things, Descartes seems to believe there is a strong possibility of their existence because they are the objects of pure mathematics. Descartes can clearly see in his mind the idea of a triangle, but he is not able to envision a chiliagon in the same way. Descartes claims that it is not a question of understanding as it is a question of conceiving. He believes that his ability to conceive and imagine mathematical concepts depends on material things that are distinct from him. Therefore, Descartes also accepts that his body exists because he “can think of no other way of explaining imagination that is equally appropriate” (49). Other things like colors, taste, and pain, which originally derive from the senses, also come back. Indeed, all external things that he doubted are all called back into existence.
In contrast to Meditation One, imagination appears to be the reason why Descartes is able to recall everything he previously doubted. Anything Descartes is capable of imagining, by definition, God is able to create. Therefore, corporeal things can exist again because Descartes imagines them in his mind’s eye. Even sensible things like pain and sight, which he cannot explain through pure mathematics, exist because Descartes has vague ideas about them. Sensation also seems to be trustworthy again because Descartes can “perceive these things better by means of the senses, from which, with the aid of memory, they seem to have arrived at the imagination” (49). Reason dictates the sensing exists because there is no other explanation for Descartes being able to perceive sight, sound, and pain and especially since they “are produced without my cooperation and often even against my will” (51). From this argument, Descartes rationally shows how his body must also exist. Descartes considers the body a faculty for receiving and knowing the senses, without which he cannot explain how is able to sense physical and material things. It is because of this “commingling of the mind with the body” that Descartes can trust what he imagines he feels, sees, and and hears (51).
By the end of the Meditations on First Philosophy, Descartes has in fact brought back everything he initially called into doubt. The only major difference between the first and sixth Meditations is the reason Descartes uses to first doubt and then to re-establish the existence of material things. In Mediation One, the knowledge founded through the senses was doubtful and untrustworthy, but more specifically, Descartes had a problem with sensing. Instead in Meditation Six, it is through the power of imagination that Descartes finds he can trust corporeal things. According to Descartes, imagination is both a mode of thought and a faculty of the mind, but at the same time it deals with things that are separate and distinct from the mind. There is a strong implication from both Meditations that the starting point from which Descartes builds up his knowledge is important. The flow of knowledge has to start from the right direction. For instance, sensations occur outside the body whereas imagination comes from within the mind. Descartes wants his opinions to start from within his mind and work outward, and this is how Descartes is able to defend against doubt.
In both Meditations, the existence of God also weighs greatly on Descartes’s decision to trust material things. In the first Mediation, God is considered to be deceiving and imperfect, and therefore, Descartes can doubt everything. By the sixth Meditation, God’s power and presence is reaffirmed, and now suddenly everything is called back into existence. Descartes, whose mission was to prove the existence of God, also ends up proving through God how all material, sensible, corporeal, and composite things are real. God is essentially the reason Descartes is able to trust his imagination, which he uses to show in the sixth Meditation that everything naturally exists. In the end, it appears like the true reason, which drove Descartes to both doubt and re-establish material things, depended all along on God’s existence. It is now safe to say that Descartes did indeed come full-circle in his argument. The reason he gives for doubting material things is the same as the reason to trust them again; the only difference being which mode of thought Descartes uses to prove their existence.