René Descartes is considered to be the father of modern philosophy. Known arguably for the most famous words in the history of philosophical thought, “I think therefore I am“. He uttered these words in his pursuit of a theory of knowledge that could dispel conclusively the skeptics claim that true knowledge is not possible. As a rationalist he held that only the mind could discover knowledge that is beyond doubt, with a certainty on par with mathematical concepts. He held the senses were not to be trusted to deliver such knowledge. A view contrary to what empiricists such as Locke and Hume held, that only experience, our senses, could give us knowledge of the world. To do this he came up with his method of doubt which was to doubt anything that could be false or was not necessarily true (such as the existence of an actual world outside of his mind). For example he doubted the physical world exists because he could be deceived by an evil demon, or the more modern version which is he could be a brain in a vat that is stimulated by a mad scientists to have the perceptions of a world – either way senses are not reliable according to Descartes. He eventually reached a belief that he thought was impossible to doubt – his own existence as a thinking thing! Hence I think therefore I exist. His existence would then provide the foundation upon which he could build a theory of knowledge that would provide knowledge with certainty.
Clear and distinct ideas essential to critical thinking
“If when I don’t perceive the truth vividly and clearly enough I simply suspend judgment, it’s clear that I am behaving correctly and avoiding error. It is a misuse of my free will to have an opinion in such cases: if I choose the wrong side I shall be in error; and even if I choose the right side, I shall be at fault because I’ll have come to the truth by sheer chance and not through a perception of my intellect”
(1) The first was never to accept anything as true if I didn’t have evident knowledge of its truth: that is, carefully to avoid jumping to conclusions and preserving old opinions, and to include in my judgments only what presented itself to my mind so vividly and so clearly that I had no basis for calling it in question.(2) The second was to divide each of the difficulties I examined into as many parts as possible and as might be required in order to resolve them better.(3)The third was to direct my thoughts in an orderly manner, by •starting with the simplest and most easily known objects in order to move up gradually to knowledge of the most complex, and by stipulating some order even among objects that have no natural order of precedence.(4) And the last was to make all my enumerations so complete, and my reviews so comprehensive, that I could be sure that I hadn’t overlooked anything.
Why we make errors in our thinking – The will over steps it’s limits
“Well, then, where do my mistakes come from? Their source is the fact that my will has a wider scope than my intellect has, so that I am free to form beliefs on topics that I don’t understand. Instead of behaving as I ought to, namely by restricting my will to the territory that my understanding covers, that is, suspending judgment when I am not intellectually in control, I let my will run loose, applying it to matters that I don’t understand. In such cases there is nothing to stop the will from veering this way or that, so it easily turns away from what is true and good. That is the source of my error and sin.“