The full name of the book is: "Discourse on the Method of Rightly Conducting One’s Reason and of Seeking Truth in the Sciences".

Descartes is a very notable French philosopher that lived in the first part of the 17th century. He's made huge contributions to both philosopy and mathematics. In philosophy, he laid down the foundations of rationalism, and thus is considered one of the fathers of modern philosophy. In mathematics, he discovered analytical geometry, the Cartesian coordinate system, the law of conservation of momentum and made substantial progress in optics and the early foundations of calculus.

The "Discourse on the Method" is the first philosophical work Descartes has published, at the age of 41 (although he's apparently completed it much earlier). It's a rather small book that takes a couple of hours to read, which makes its importance and fame even more remarkable.

Part 1 serves as an introduction. Descartes presents himself as having "an average mind". In spite of this, he is clearly happy with choosing a path in life that directs him to pursuit knowledge and self improvement:

I will not hesitate, however, to avow my belief that it has been my singular good fortune to have very early in life fallen in with certain tracks which have conducted me to considerations and maxims, of which I have formed a method that gives me the means, as I think, of gradually augmenting my knowledge, and of raising it by little and little to the highest point which the mediocrity of my talents and the brief duration of my life will permit me to reach.

He provides an auto-biographic background, telling about his early life of "reading the letters" (writings by scientists and philosophers of the past). Left utterly unsatisfied with the answers he's found in these books, he decided to engage on a different path for obtaining knowledge and understanding of the world, and spent a few years traveling around Europe, "learning the customs and conversing with different people".

It is useful to know something of the manners of different nations, that we may be enabled to form a more correct judgment regarding our own, and be prevented from thinking that everything contrary to our customs is ridiculous and irrational, a conclusion usually come to by those whose experience has been limited to their own country.

Especially, he was dissapointed with the readings of philosophy:

Of philosophy I will say nothing, except that when I saw that it had been cultivated for many ages by the most distinguished men, and that yet there is not a single matter within its sphere which is not still in dispute, and nothing, therefore, which is above doubt

Part 2 begins by a long metaphor that Descartes uses to explain how he planned to overthrow the knowledge he gained from the books and replace it with a fuller understanding of the world, collected from his travels and reflections.

He eventually comes to one of the most famous parts of the book, "The Method", which consists of 4 parts:

The first was never to accept anything for true which I did not clearly know to be such; that is to say, carefully to avoid precipitancy and prejudice, and to comprise nothing more in my judgement than what was presented to my mind so clearly and distinctly as to exclude all ground of doubt.

The second, to divide each of the difficulties under examination into as many parts as possible, and as might be necessary for its adequate solution.

The third, to conduct my thoughts in such order that, by commencing with objects the simplest and easiest to know, I might ascend by little and little, and, as it were, step by step, to the knowledge of the more complex; assigning in thought a certain order even to those objects which in their own nature do not stand in a relation of antecedence and sequence.

And the last, in every case to make enumerations so complete, and reviews so general, that I might be assured that nothing was omitted.

Note that it is an early exposition of the "problem solving" methods so celebrated today by authors that manage to write whole books with less substance than contained in the quote above.

Descartes then notes that an accurate observance of these rules enabled him to solve a few interesting scientific problems. Indeed, one of his examples of the application of "The Method" appeared in the appendix of the book and served as a basis for calculus.

Descartes begins Part 3 with another list, a "code of morals" which he set for himself to live by "in the mean time", while he's using the method to think of a new approach for life. In short, he avows to:

  1. Obey the laws and customs of his country, and try to behave according to "the most moderate opinions, and the farthest removed from the extremes". This is one of many places in the book in which Descartes expresses his carefulness of surfacing new and radical ideas. It makes a lot of sense if you consider the period in which he lived, when the church ruled and opposed all "new and radical" ideas.
  2. To be firm and resolute in one's decisions. Even if they've been decided under difficult conditions with lots of unknowns - once the decision is made, stick to it.
  3. To conquer oneself by adopting the desires to the world rather than wishing it to be the other way. Note how similar this is to Ayn Rand's first principle of metaphysics. Descartes laid the foundation of rational thinking upon which lays a whole philosphic framework of many centuries forward.
  4. He decided to review all the "different occupations of men in this life, with the view of making choice of the best". In this quest Descartes reached the conclusion that I could not do better than continue in that in which I was engaged, viz., in devoting my whole life to the culture of my reason, and in making the greatest progress I was able in the knowledge of truth, on the principles of the method which I had prescribed to myself.
Part 4 has several interesting points. It begins with the famous:

I observed that, whilst I thus wished to think that all was false, it was absolutely necessary that I, who thus thought, should be somewhat; and as I observed that this truth, I think, therefore I am (COGITO ERGO SUM), was so certain and of such evidence that no ground of doubt, however extravagant, could be alleged by the sceptics capable of shaking it, I concluded that I might, without scruple, accept it as the first principle of the philosophy of which I was in search.

He also reasons about the separate existence of body and soul, reaching the conclusion that the soul must exist and be immortal. Then, he uses the ontological argument to "prove" that God exists, by claiming that the fact that he can clearly perceive that he's not perfect, and can think of a more perfect being than himself, it clearly must be God, because otherwise who could have implanted in him this perception of perfection beyond his own ?

Naturally, these days this argument sounds hardly convincing. But it makes sense in the historical context Descartes lived in, when people were born and raised into intense religion and were nurtured and schooled with a dogma that left no doubt in their minds of the existence of God. Otherwise, it's difficult to see how Descartes, who openly proclaimed the ability of his pure reason to perceive this world could have so easily fallen to a deeply flawed argument that doesn't make much sense from a rationalistic point of view.

Part 5 is mainly devoted to reasoning about the structure of our bodies, and of the bodies of animals, whereby the author attempts to expound on the "clear" separation of body and soul. He engages in a long and quite dull description of how an animal heart works, after which he reaches the subject of how machines could perhaps fake the functions of the body but in no way of the soul.

Amazing insight from Descartes, in the 17th century to presuppose the creation of machines that can behave and talk like humans! Of course, his reasonings on the innate difference in the souls of humans and animals have recently been overthrown by experiments with apes that show intelligence and can converse with people using specially designed sign languages and computers. But still, it can be said with confidence that he conceived an equivalent of the Turing test of intelligence, 400 years before Turing.

Part 6 was written 3 years after the others, and in it Descarts explains the reasons that have prevented him from publishing the work. He speaks of "another individual" who has published "a certain doctrine in physics" which didn't seem controversial to Descartes but raised great opposition. I don't know if it's related, but Galileo Galilei has published one of his first works in 1610 and raised great controversy with the church. The times Galilei and Descartes lived in were not good for scientific discoveries, and Descartes's caution can be easily understood.

Nevertheless, he continues to raise many reasons for publishing The Method, which he did indeed publish, eventually.

Well, it's time to conclude the review. I think that in order to be trury appreciated, this book must be viewed in historic context. The ideas Descartes present hardly catch anyone by surprise today, because they're mostly maxims generally accepted today, at least amongst people of scientific inclination and rationalists. But what's truly impressive is that his ideas are the basis of these maxims, the foundations on which most of modern philosophy lays.

So if you're looking for a book to expand your horizons, this hardly is it. But if you're interested in the history of philosophy, or in turn, like me, seek to start any path of learning from the basics, you probably won't be dissapointed with spending 2-3 hours on reading this book.