no need of vain hypotheses, as is the case in matters inaccessible to sense and open to doubt. Concerning these, if one essay to speak, one must resort to hypothesis. So, if one should speak and entertain an opinion touching things in the heavens or under the earth, it would be clear neither to the speaker nor to those who heard him whether his opinion was true or false; for there is no appeal to aught that can establish the truth." 8
The tract proceeds to show that the art of medicine has grown through observation of the needs and diseases of men, — not through the acceptance of some hypothesis as to their cause. 9 For example, the regulation of the
patient's diet, especially in acute illness, was fundamental in Hippocratic medicine. And the tract argues that no improvement in diet, even for people in health, could have come about except through observation of the ill effects of unsuitable food. Much more, then, has long clinical experience shown the need to modify the regimen of a patient suffering from a fever. Indeed nothing has so promoted the art of medicine as observing how the food for a healthy man injures the sick, and the consequent endeavor to regulate the patient's regi-
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