This is the first in a series of posts called PHI 101 where I will be taking a look at several philosophers and philosophical ideas from a Christian perspective.

Descartes is widely regarded as the most important philosopher in the European Enlightenment. He is also considered by many to be the dividing line between ancient and modern philosophy. Because his ideas have been so influential, it is important that Christians understand them and how they have influenced the worldviews that are present in our culture. I will limit my discussion here to two of his main ideas and their consequences: skepticism and the cogito.

Skepticism

Descartes begins his Meditations on First Philosophy, with a rather commonplace observation. However, if you take the time to stop and think about this simple fact, it is quite disturbing. He observes that in the past, he has often been mistaken. It seems absurd, perhaps, that we should even talk about this. Of course people are mistaken all the time. However, if we allow this possibility, then what is there to assure us that our current set of beliefs or knowledge is correct?

Because of this observation, Descartes starts his philosophy by throwing out any belief which could be called into question. The key idea here is that we must be absolutely certain of something before we can say that we know it. He then makes a clean slate of all his beliefs by supposing that it is possible that there is some sort of evil demon that has deceived every one of his senses and ideas about the world. It is not necessary for this demon to actually exist, simply the possibility of its existence is enough to make him doubt.

An easy way to understand what Descartes is doing in this discussion is to ask yourself honestly, “How do I know for certain that right now I am not dreaming?” If you consider this, it throws into question all of existence and everything you think you know. It makes you look further than common sense for the real foundation of your beliefs.

This is useful for Christians because many people live in this place of skepticism. They are not truly convinced of anything and have no firm epistemological foundation. As Christians, we must evaluate the strength of our own beliefs and know for certain why we put all of our trust in God. Here is an interesting question to investigate the real reasons for your faith, “Even if I were dreaming right now, would I still know that God exists?” In other words, does your faith in God rest on your experiences of the world? Does it depend upon some fact about which you could be deceived? When an atheist asks you, “Why do you believe in God?”, it would be good to have considered this matter.

The “Cogito”

Fortunately, Descartes does not leave his readers in a place of total skepticism for long. He soon finds a principle that he could never be deceived about. His argument is that even if there were some sort of all-powerful demon deceiving him about everything, there would still be a ‘him’ to deceive. This leads to the famous Latin phrase which appeared in his Discourse on Method, “cogito ergo sum.” This is translated “I think therefore I am” which most of you have probably heard before. Another way of phrasing this is to say, “I can be mistaken about things. However, if I am mistaken then I am thinking. If I am thinking then I must, at least, exist.”

This is a very powerful argument. Descartes has established a firm foundation for believing something, and from there he can work his way to other pieces of knowledge. This idea is so powerful that it has easily worked its way into the worldviews of many people around us everyday. For most people, the foundation for their knowledge is a faith in themselves.

A classic criticism of Descartes’ argument here is the fact that “I think therefore I am” has the hidden premise that “all things with the property of thinking exist.” This premise itself would have surely been thrown into doubt along with everything else. This gets at the heart of the matter. Any argument, whatsoever, must rest on some understanding of truth. As Christians we derive our entire philosophy from the foundation of God and who he is. This gives us a basis for making claims about truth. If we were to base our entire philosophy on the ground that we exist, this would give us no firm ground from which we could make truth claims of any kind.

I hope these observations about philosophy have challenged your way of thinking and better equipped you to engage a world that does not know Jesus Christ, the way, the truth, and the life.