Book 1
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Since of the divisions of the Art of Medicine, the one which heals diseases, as it is the most difficult, is also the most famous, we must speak about it first. And because there is a primary difference of opinion, so holding that the sole knowledge necessary is derived from experience, others propounding that practice is not efficient enough except after acquiring a reasoned knowledge of human bodies and of nature, I must indicate which are the principal statements on either side, so that I may the more easily interpose my own opinion also.
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They, then, who profess a reasoned theory of medicine propound as requisites, first, a knowledge of hidden causes involving diseases, next, of evident causes, after these of natural actions also, and lastly of the internal parts.
