Descartes’s Philosophical Method

The medieval age of faith in one, more or less complete, system of beliefs (based primarily on the Bible and the works of Aristotle) started to collapse with the work of such people as Martin Luther (1483-1546), Nicolaus Copernicus (1473-1543), Galileo Galilei (1564-1642) and René Descartes (1596-1650).

 

Luther was a devout Catholic who was expelled from the Church because of his public criticism of some of its teachings and practices.  From then on Western European Christians could not simply rely on the authority of the Church, they had to choose: Catholic or Protestant?  Against the authority of the system, Luther said that, “every believer is a priest.”

 

Copernicus theorized that the Earth revolved around the Sun, and was not the center of the world as the Church taught.  Galileo offered proof that Copernicus was right, and said that: “In questions of science the authority of a thousand is not worth the humble reasoning of a single individual.”

 

Descartes applied this new, individual thinking to philosophy.

 

He opposed arguing from authority, i.e. arguing or claiming that something must be true simply because some supposed authority (Aristotle, the Bible, Dr Richter, etc.) had said it was true.

 

Descartes favored rationalism, the approach to philosophy based primarily on reason, not experience or experimentation.

 

(The opposite approach is called empiricism.)

 

Rationalists look for a priori knowledge.  Literally this means knowledge that can be had prior to all experience, but really it means truths that can be known purely by reasoning.  For instance, we know that 1 + 1 = 2 not because of experience or some experiment done in a laboratory, but just by thinking about numbers and addition.  To know that bachelors are not married you do not need to do field research on bachelors.  You just need to think about the concept ‘bachelor’.  Even if you know that 1 + 1 = 2 only because someone told you, it is still a priori as long as someone could figure it out in their head.

 

Empiricists think that a priori knowledge is pretty trivial, and instead focus on a posteriori knowledge.  Literally this means truths that can be known only after some experience, but really it means truths that cannot be known just by thinking alone.  A posteriori truths could even be known before any relevant experience, for instance if God miraculously revealed the future to you.

 

Descartes and the other famous Rationalists believed that a priori knowledge that was not trivial could be gained by thinking about our innate ideas, i.e. ideas that we are born with.  These might be conscious or unconscious, fully formed or more like seeds of ideas we are likely to develop later, mere concepts (like words) or full beliefs (like sentences).

 

Descartes was not a skeptic, but he used skepticism against itself with his method of doubt.  Anything that could be doubted, he set aside, so that only rock-solid certainty remained.

 

It would take too long to consider each individual belief, so Descartes examines categories of belief, starting with beliefs based on sensory data.  He doubts all of these, since the sense sometimes misinform us.  Indeed, he thinks, all his sensory experience might be like a dream or hallucination.

 

This is hard to believe, even as a possibility, though.  To aid his imagination Descartes pretends that he has been created by an evil genius or demon.  The evil demon, he imagines, has given him the worst possible mind and devotes his life to deceiving the mentally feeble Descartes.

 

Now even his a priori reasoning is in doubt.  Like a wrongly wired calculator, even his simplest acts of reasoning might lead him to the wrong conclusion, and he might be too stupid to realize it.

 

Must everything be doubted therefore?

 

No.  To be deceived, or to doubt, or to think anything at all, Descartes argues, he must exist.  Cogito ergo sum: I think therefore I am.

 

This does not mean that thinking causes Descartes’s existence.  His point is not about metaphysics (the study of the ultimate nature of reality) but about epistemology (the study of knowledge, or theories about knowledge).  He knows that he exists because he knows that he thinks. 

 

So he exists.  And what is he?  He might be anything, but whatever he is, he must be a thinking thing.