Rene Descartes (1596-1650) was both a philosopher and a mathematician; a rationalist who only believed in reason. Descartes wanted to build a philosophical system from the ground up, rather than relying on the work of others. “The father of modern philosophy” Interested in “certain” knowledge and the relationship between the body and the mind. Descartes was not a total skeptic. There must be a connection between the body and consciousness, but they are not exactly the same. (Sort of like Plato’s belief in separation between body & soul.) Believed in a philosophical system that goes from simple to complex. Descartes realized that you can’t trust your senses. But, he realized that he did doubt his own senses. In order for him to be able to do that, he must exist. Thus, we have “I think, therefore I am.” What else could he perceive? a perfect entity, God. Descartes felt that the idea of God was innate and therefore also exists. The more self-evident something is to one’s reason, the more certain he was that it must exist. After that quantitative properties (weight, etc.) were deemed okay, but qualitative ones were not. However, there is an outer reality because a perfect God would not deceive us. God’s guarantee – what we perceive with reason corresponds to reality. Descartes thought of two realities: thought & matter. These two have no contact with each other. Thus, Descartes was a dualist. Animals belong completely to extended reality, but man is a dual creature. Bodily processes obey laws of matter. But, the mind is independent of extended reality. According to Descartes the mind can be affected by the physical, but it can also detach itself.
To know more about the philosophy of Rene Descartes you can go to our overview and summary of Descartes' philosophy. If you want to get to know specific works by Descartes you can go to our summaries of his Discourse on the method or Meditations on the First Philosophy (or the extended summary by chapter of Meditations on the First Philosophy).