Question: I was reading about Descartes and I don’t really understand what he means by “I think, therefore I am.” Could you explain this to me?
Reply: René Descartes’ Latin grounding for rationalist certainty is “cogito ergo sum,” otherwise known as “I think, therefore I am.” This deceptively simple conclusion is identified as a distillation of rational truth away from the confines of perceptual experience. Descartes got going in philosophy by way of mathematics and science. He was particularly interested in the apodictic certainty of mathematics and by extension how this type of necessary truth certainty governs the laws of science. Descartes was inspired to this goal due to the previous lack of identifying a whole and reliable basis for certainty with Scholastic (Aristotelian empiricism). All of this is to point out that if one desires to ground mathematical-like certainty, we must ground such certainty within the conscious way in which we get going with mathematics and science. To be clear, when we seek the whole of rational certainty, we must work to locate certainty in our thinking that is often partially obscured by perception.
To get to this aim of certainty, Descartes developed a mode of skepticism that deployed doubt as a way to clear the path away from perceptual knowledge alone. If the senses cannot be trusted, then Descartes must make absent all perceptual doubt to achieve the goal of finding and locating pure rational certainty (the very core of how we presently constitute and identify certainty in our investigations of truth). To get to the basis of rational truth, we must locate the presence of our understanding of rational truth within the individual manner of conscious thought by which our understanding of rational and universal truth is absolutely grounded. This manner of conscious thought is his “cogito ergo sum.” This is the manner of conscious by which we can ground truth. “I think, therefore I am” is what is presently left over after all perceptual doubt is put aside and made absent. This was true for Descartes, as it is present to my consciousness as I write this. Likewise, we must consider this to be a grounding for our acquisition of certainty—rational certainty. If the whole of rational thought is identified from the certainty of the “cogito ergo sum” then this indicates an ego that is thinking. If I am the one who is doing the thinking, this has within it the rational necessity of a being who consciously alive (an ego) that is thinking. Existence must be present to me in order to think rationally. This makes rational sense given that we cannot identify certain thought outside of our existing consciousness (certain truth for Descartes cannot be identified in perception alone). Rationally, the ego also is a presently centered point not only for me, but it also must be presently centered for every other rational creature who seeks certainty.
Descartes’ “cogito ergo sum” locates rational certainty to be found when perception is eliminated as a candidate for the source of rational truth. Descartes’ skepticism has the aim of clearing the way for rational certainty to become a ground for philosophic inquiry inspired by the necessary certainty of mathematics. Let me know if this helps!