Discourse on Method and Meditations on First Philosophy - René Descartes
…there is less perfection in works made of several pieces and in works made by the hands of several masters than in those works on which but one master has worked. Thus one sees that buildings undertaken and completed by a single architect are commonly more beautiful and better ordered than those that several architects have tried to patch up, using old walls that had been built for other purposes. pg. 7, Discourse on Method, Part Two
Upon that premise, Descartes casts aside the philosophy that had evolved for almost a millennia prior and starts over. He accepts nothing as true unless it proves to be firm and certain so that there is no occasion to put it in doubt. In this void, he describes how he comes upon his foundational premise. That one that’s on all the bumper stickers and punned for coffee mugs. From there he builds his argument for the existence of God.

Discourse briefly summarizes his process and Meditations walks through the thinking. Descartes seems to be simultaneously revered and dismissed today. And I can see why. He writes plainly and in a genuine effort to communicate his process. His willingness and discipline to reconstruct his world based on self-reflection is an admirable example of the” unexamined life is not worth living” call. And, though it is become so ubiquitous that it has lost a lot of resonance, the “I think therefore I am” premise is one of the soundest conclusions there is in all the philosophy leading up to his time. Probably after, too, but I’ve got some more reading to do before I can be comfortable with that claim.

The downside? After coming to his brilliant premise, his argument for the existence of God falls on a whole set of presuppositions. Presuppositions which he had been so diligent in discarding in the first place. From there, the foundation begins to shift and his logic bunker becomes more of a temple. But take this comment cautiously. Prior to publishing Mediations on First Philosophy, he sent out the work to others eliciting there comments. Those objections and replies were published separately. In the “Preface to the Reader” in Meditations, he “earnestly entreat the readers not to form a judgment regarding the Meditations until they have deigned to read all these objections and the replies I have made to them.”

That’s fair enough. I think Descartes was probably a pretty awesome guy.