Preface to the French edition Descartes asked Abbot Claude Picot to translate his Latin
Principia Philosophiae into French. For this edition, he wrote a preface disguised as a letter to the translator, whose title is "
Letter of the author to the translator of the book, that may be used as a preface." This was published in 1647, when he was 51 years old and in the mature, final period of his life. In this writing, Descartes provides some reflections on his ideas of wisdom and philosophy. Its content may be summarized as follows: ;Concept of philosophy Philosophy is the study of
wisdom, understood as the ability to conduct the human activities; and also as the perfect knowledge of all the things that a man can know for the direction of his life, maintenance of his health, and knowledge of the arts. Only God is perfectly wise, and the man is more or less wise, in proportion to the knowledge he has of the most important truths. ;The degrees of knowledge Descartes identifies four degrees of knowledge which he names
common, and a fifth degree he designates
higher. The first degree consists of clear and evident notions that can be acquired without the need for any meditation. The second degree is all that is learned by means of the senses. The third comprises what we learn when talking with others. The fourth consists of what we can learn from the writings of those capable of giving good instructions. ;Higher wisdom There have been great people throughout history who have pursued a better and more secure wisdom, a
fifth degree of knowledge. This has consisted of the search for the
first causes, and those that have followed this pursuit have been named
philosophers, but he thinks that none have yet been successful. ;Doubt and certainty Since
Plato and
Aristotle, there has been discussion on doubt and certainty. Those that have favoured doubt have arrived at extremes of doubting even the most evident things, and those that have sought certainty have relied excessively on the senses. Though it has been accepted that the senses may mislead us, according to Descartes, nobody had yet expressed that the truth can not be based on the senses, but in the
understanding, when it is founded on
evident perceptions. ;Meditations on first philosophy The search for the first causes, or basic truths, as undertaken by Descartes is contained in this work. It explains the
metaphysical principles on which to build the rest of knowledge. ;The tree of philosophy Descartes describes philosophy as like a tree, whose roots are
metaphysics, its trunk
physics, and the branches are the rest of the sciences, mainly
medicine,
mechanics, and
morals that is the last level of wisdom. In the same way that trees have fruits in their outer parts, the usefulness of philosophy is also contained in the areas that stem from its foundation.
Body of the work There are four parts: • Part I. - of the Principles of Human Existence • Part II. - of the Principles of Material Things • Part III. - of the Visible World • Part IV. - of the Earth. == Copies and modern editions ==