Three years ago...I learned that people to whom I defer, and whose authority over my actions is hardly less than that of my own reason over my thoughts, had disapproved of a hypothesis in the field of physics that had been proposed somewhat earlier by another person. I do not want to say that I had accepted that hypothesis...This occurrence was enough to make me change my resolution to publish the treatise...

(Knowledge of "bodies" in the sense of matter) would not only be desirable in bringing about the invention of an infinity of devices to enable us to enjoy the fruits of agriculture and all the wealth of the earth without labor, but even more so in conserving health, the principal good and the basis of all other goods in this life. For the mind is so dependent upon the humors and the condition of the organs of the body that if it is possible to find some way to make men in general wiser and more clever than they have been so far, I believe that it is in medicine that it should be sought. It is true that medicine at present contains little of such great value; but without intending to belittle it, I am sure that everyone, even among those who follow the profession, will admit that everything we know is almost nothing compared with what remains to be discovered, and that we might rid ourselves of an infinity of maladies of body as well as of mind, and perhaps also of the enfeeblement of old age, if we had sufficient understanding of the causes and of all the remedies which nature has provided.

-Descartes, Discourse on method part 6.