Descartes claims that he generally feels no inclination to publish his views. However, the success he has had with his method and his principles of physics suggests to him that they could prove an enormous benefit to mankind if made public, particularly when applied in the fields of engineering and medicine. Because he is incapable of fully exploring all these fields by himself, he had hoped that in making his findings public he would enable others to contribute as well. Positing God as the first cause of everything that is, and using his method, it is not difficult to come up with explanations for most straightforward observations. Deducing the many particularities of earthly phenomena, however, requires careful study and observation, and Descartes hopes many specialists will contribute to this cause.

However, he decided not to publish his principles of physics (as expressed in The World) because he fears the controversies they may arouse may distract him from his work. He continues to record carefully all his observations and discoveries, however, and intends to have them published after his death. That way, he may work uninterrupted during his life, and posterity may benefit from his discoveries. All his progress to date has resulted from overcoming only five or six difficulties, and he expects that he may overcome all his remaining difficulties within his lifetime if only he can stay free from controversy.

People might object that by publishing his views Descartes will allow others to identify possible errors in his writings and to develop new directions that Descartes had not thought of. However, Descartes replies, he has yet to hear a plausible objection that he has not himself already anticipated. Further, he does not feel he has taken his investigations far enough that others can develop new directions from it. Even the people with the best minds—people who are capable of philosophical speculation—may not benefit from his work as it stands. If they prefer to appear knowledgeable rather than confessing their ignorance and working toward the truth, they will not want to follow his method. And if they do hope to gain knowledge for themselves, they won't want to use his findings but pursue their own investigations. Help can often be a nuisance and a hindrance, and Descartes is happier working alone and free from controversy.

For these and other reasons, Descartes decided three years ago not to publish the principles of his physics. However, he has come to publish this work, along with the appended essays (see the Context file) for two reasons. One is to dispel any rumors that his discoveries are false, and the other is because he feels he needs the help of other scientists if his work in certain fields is to advance. He hopes that people will examine his essays in optics, meteorology, and geometry, and he promises to publish any worthwhile objections to these essays, along with his replies, in a future edition of the work.

Descartes remarks that the "suppositions" that serve as first principles in his essays are not argued for, but he feels that they are made evident by the results that follow from them, just as those results are made evident by the suppositions. He believes these suppositions can be deduced from his first principles, but, for the reasons stated above, he does not wish to make this deduction publicly.

Having explained his reasons for writing in French rather than Latin, Descartes closes by expressing his plans to devote the rest of his life to scientific study without hope for fame or profit.