Epistemology of Rene Descartes
Rene Descartes’ epistemology was driven by his desire for certainty. Unfortunately, he did not find the sort of certainty that he was looking for during his scholastic training at the Jesuit college of La Flèche. The abstract theological debates of his time appeared to yield an intolerable amount of disagreement. In contrast, however, the blossoming fields of mathematics and physics appeared to have the potential for silencing endless controversies. Descartes thought the simple elegance and the clear deductive moves found in the science of mathematics would yield a more promising method of inquiry than he had found in his scholastic training.
Descartes also sought to bring unity to the sciences. Rather than having a diversity of methods for studying different objects, Descartes wanted to streamline the scientific process. His own discoveries were very valuable to his project, for he had shown how geometric figures could be represented in the form of algebraic expressions. If geometric figures could be described in this way, then perhaps everything could be analyzed by means of the same method of inquiry. He hoped that, by universally applying this method, he could bring certainty and unity to the sciences.
Descartes’ primary criterion for the truth of an idea was the “clear and distinct” criterion. He thought that, as a general rule, whatever he could perceive very clearly and distinctly was true. For Descartes and other rationalists, the primary source of truth is found inside the mind. One does not find certain knowledge in the ever-changing flux of the senses; rather, one finds certainty by exploring the contents of the mind. But even here, one has to be careful because not all thoughts are equal in their reliability. It is only the very clear and distinct ideas that provide us with the kind of certainty for which Descartes was looking. His aim was to find a clear and distinct idea that could not be subject to doubt.
Descartes used the method of mathematics and the criterion of clarity and distinctness to search for truth. Since geometry must work from an axiom or starting point, Descartes sought to find a solid starting point from which to begin his philosophical task. However, in order to find a solid axiomatic starting point, he would need a method in order to find it. His method for this task was radical doubt.
Descartes believed that if he used doubt as a method, he could cleanse himself of all his fallible beliefs. To that end, he subjected his most fundamental beliefs to the cleansing effects of his method. He hoped that his doubt would uncover the bedrock idea upon which he might build his philosophy. The bedrock idea which he found was this: “I exist,” is necessarily true whenever it is put forward by me or conceived in my mind.
With this as a starting point, Descartes set out to prove the existence of God. If God existed, he reasoned, God would not deceive him or allow him to be deceived into thinking that an external world existed when in fact it did not exist. Given the fact that our perceptions of the material world appeared to be outside of our control, and given the fact that a good God who would not allow us to be deceived concerning these appearances existed, it followed that our perceptions of the world was caused by material things in the world.
In sum, Descartes doubted his fundamental beliefs to arrive at a certain starting point. He then argued from the fact that he existed as a thinking thing with an idea of God, to the fact that God exists. Since God exists and He would not allow Descartes to be deceived about the external material world, Descartes concluded that he could, in fact, have knowledge of things in the material world.
Metaphysics of Rene Descartes
The way in which he argued for certain knowledge of the material world produced a form of metaphysical dualism. In the Meditations on First Philosophy, Descartes says that the fact that he can clearly and distinctly understand one thing apart from another is enough to make him certain that the two things are distinct. For Descartes there was the world of the mind and there was the world of inert matter. Since he could clearly and distinctly understand himself as a thinking thing wholly apart from his material constitution, he concluded that this must be due to the fact that there are two separate substances: a mental substance and a physical substance.
As he considered the mind, he realized that its properties are substantially different from the properties of physical bodies. Minds are not extended in space, but physical bodies are. Minds are able to reason and doubt; physical bodies cannot do either of these things. Minds do not operate mechanistically, but the physical world operates mechanistically. As the list of essential differences grew, his certainty that there was a mental substance and a physical substance became solidified.
This separation between mind and matter brought up the question of the relation between two separate substances that have nothing in common. Descartes seemed to think that they could interact. He recognized that what he understood to be the body affected the mind and that what he understood to be the mind affected the body. Even if he could not show how the two interacted, he believed that he knew that they did interact.
One final feature of Descartes metaphysics should be mentioned. In his Meditations, it is mentioned that he thought that our existence was a sort of intermediate existence. He thought of existence as a spectrum where God was on one end of the spectrum and nothingness was on the other end. This metaphysical position is how Descartes accounted for error in our judgment. God is perfect in every possible way. As one moves down the spectrum of existence, defects creep into being. Since humans are lower on the scale of existence, humans are able to make errors in judgment. This feature of Descartes philosophy curiously finds itself in later rationalist philosophers.