First published in 1489, De Vita Libri Tres comprises three volumes: the first book is about physical health, the second is about prolonging life, and the third is about astral influences. The work focuses not on the soul or body, but on the spiritus, which is described early on:

"Only the priests of the Muses, only the hunters after the supreme good and truth are so negligent (alas) and so unfortunate that they seem utterly to neglect that instrument by which they can, in a way, measure and grasp the whole world. An instrument of this sort is the spirit, which by the physicians is defined as a certain vapour of the blood, pure, subtle, hot and lucid. And, formed from the subtler blood by the heat of the heart, it flies to the brain, and there the soul assiduously employs it for the exercise of both the interior and exterior senses. Thus the blood serves the spirit, the spirit the senses, and finally the senses reason."

The book's thrust depends on the tension Ficino tries to resolve intellectually—a tension that is typical of the syncretism of much of the early Renaissance—between Classical philosophy and Christian belief. By filtering both through the cosmology of Plato, Ficino attempts to reconcile these world-views. De Vita is also an amalgam of philosophy, medicine, magic and astrology.

The present edition includes a substantial introduction with its own notes and index, a critical text, a translation, notes, a general index, an index of materia medica, and a list of primary and secondary works cited. The critical text is based on the first edition of 1489 and its errata sheet; it gives every variant from the manuscripts which has any claim to being authorial.

Marsilio Ficino (1433-1499), was a leading thinker in Florence, a magnet for the most brilliant scholars of fifteenth-century Europe, where the Italian Renaissance derived its impulse and direction, and where the West was awakened to a new realization about itself. In devoting most of his life to the study and translation of the great dialogues of Plato and the Neoplatonists, Ficino and his colleagues were midwives to the birth of the modern world.