The classical way of thinking was that what we know first, and best is what we perceive with our senses. Rene Descartes was a revolutionary philosopher because he went against the classical Aristotelian way of thinking. Descartes stated, that what we know through the senses is more doubtful then what we perceive through our own reason. .
Therefore what we know first, we know with the greatest certitude, because he does not want to believe anything else that he has learned in the past, and wants to believe what he discovers for himself. He also said that anything that we can doubt, we should not take to be true because our senses can deceive us. Descartes goes against all other ways of thinking, and believes that what we know through reason and what we learn first is what we know with the most certainty. .
The order in which we know things, according to Descartes, all stems out from his base philosophy, which is "I think therefore I am." "I think therefore I am" is the basis of Descartes's philosophy. Because "I think therefore I am" is the first thing that Descartes bases his philosophy on, and it is what he knows the greatest. Since it is the first thing that he learned, it is also the thing that he knows with the greatest certainty. We know things according to Descartes by what we know first, and since we know "I think therefore I am" first that is where we begin to learn all things according to Descartes. "In order to think, it is necessary to exist." By thinking Descartes comes to the conclusion that he does in fact exist because he thinks. If he thinks, he exists, therefore that is the order that we know things according to Descartes. We must first come to the realization that we exist because we think, and then we can begin to understand Descartes's other steps.
" That the things we conceive very clearly and very distinctly are all true." This is another of Descartes's most basic points; only take for fact what you know to be clear and distinct.