As well as developing four rules to guide his reason, Descartes also devises a four-maxim moral code to guide his behavior while he undergoes his period of skeptical doubt. This ensures that he will not have to remain indecisive in his actions while he willfully becomes indecisive in his judgments.
The first maxim is to remain faithful to the laws and customs of his country and his religion. He acknowledges that this choice is somewhat arbitrary given that he has undertaken to abandon all his former opinions and prejudices. However, he notes that if he is to get on in his own country while he dismantles his former opinions he would do well to let his actions be guided by customs of his own country rather than those of some foreign nation. Noting that there is often a difference between what people say and think and what they do, Descartes resolves to follow only the actions of those in his country who are considered most sensible. In cases of conflicting opinions as to how one ought to behave, he always opts for the most moderate option so that he is least likely to err drastically. In particular, he resolves not to allow himself to be bound to promises that would restrict his freedom to alter his judgment later.
His second maxim is to remain firm and decisive in his actions. Even a wrong decision is better than indecision, since indecision takes one nowhere. If there is no obviously true and certain decision to be made, Descartes opts for the most probably right decision, and treats that decision as if it were true and certain. Not only will this save him from never acting (since certainty is hard to find) but it will also save him from any future regrets he would experience if he were less decisive.
His third maxim is to try to master himself and not external factors, to work to change his desires rather than the world. We cannot control external events with any certainty, so we are bound to meet with disappointment if we allow our happiness to be governed by external factors. Ideally, we come to see our thoughts as the one thing we have control over, and to recognize that if even with our best efforts we cannot change something in the world, then that thing is, for all intents and purposes, impossible to change. It takes a great deal of work and meditation to achieve such mastery of the mind, but it brings greater peace and happiness than any worldly success.
His fourth maxim is to find the best possible occupation in life. He concludes that following the present method of philosophy is the best he can do. For one thing, he has found great satisfaction with it, and for another, his only motive for adopting these moral maxims is so that he can pursue this method further. Through this method, he hopes to find certainty and happiness.
Having made up his mind on these maxims, Descartes heads out into the world and spends the next nine years traveling, conversing with others, and further developing his mathematical studies. He remains detached from the business of the world, acting as a spectator, carefully uprooting all the errors or unjustified opinions in his mind and taking careful note of any experiences that he might be able to build upon. Finally, in 1629, he settles in Holland, away from people he knows, where he manages to enjoy the solitude necessary for careful study as well as all the amenities of city life.
The moral maxims Descartes puts forward in this third part are clear evidence of his Jesuit education. One of his main strategies in the Discourse, and even more so in the Meditations, is to win over Catholic, scholastic, Aristotelian philosophers by paying lip service to their traditions. The Jesuits were particularly predominant in philosophy, and Descartes owes his own philosophical education to them. If his writings are to have any impact in philosophical circles, he must be convincing to the Jesuits. The Meditations are in many ways modeled on the Spiritual Exercises of St. Ignatius of Loyola, the founder of the Jesuit order.
It is open to debate as to what extent Descartes is deeply and genuinely influenced by the Jesuits and to what extent he is paying lip service to their traditions in order to win favor with Jesuit philosophers. In the case of the Meditations, the latter is more likely true, but in the case of part three of the Discourse it would seem Descartes is genuinely impressed with Jesuit teaching. The moral maxims he sets forth bear a distinctively Jesuit imprint, but they are also profoundly good advice.
In both the Meditations and the Discourse Descartes is very careful (perhaps too careful) to remain loyal to Christian doctrine. Considering that the Inquisition has recently condemned Galileo for publishing ideas that he agreed with, Descartes had every reason to tread carefully with Christian doctrine. Thus, he is clear in his first maxim that he does not abandon the customs and morality of Catholic France. This might seem to be contrary to his stated purpose of suspending all his old opinions, but Descartes is quite careful in his wording here. He resolves to allow his actions to be guided by tradition and custom, but makes a clear distinction between his thoughts and his actions. This leaves him free (in theory) to question the existence of God and the truth of Catholic doctrine, but also insures that this doubt will not lead him to offend his fellow countrymen.
The second maxim defends the doctrine of probabilism that was upheld by the Jesuit order. Probabilism states that in cases where certainty is impossible, it is acceptable to act according to what is most probable. Descartes takes this line, suggesting that his adoption of doubt should not inhibit his actions. Again, he is drawing an important distinction between thought and action, suggesting that his methodological doubt should not keep him from interacting in the world in a healthy manner.
The third and fourth maxims both suggest that the life of the mind is more valuable than action. A balanced and peaceful mind guarantees a happy life more than any kind of earthly pleasures.
These maxims are closer to religious principles than philosophical ones. Moral philosophy is generally less concerned with developing maxims for action, and is more concerned with justifying different kinds of behavior. Moral philosophers ask: to what extent are we free to do what we want, to what extent can we be held responsible for our actions, how can we justify acting in certain ways, how can we know what is right, and so on. Descartes does not make much of an effort to justify or rationalize his maxims. This is largely because they are pre- philosophical. He is not trying to figure out what is right; he is simply developing a practical guide to help him through life until he can arrive at some more certain principles. As rules on how to live rather than philosophical puzzles, his maxims resemble the teachings of religious figures more than of philosophers.