One of the circumstances that detained Petrarch at Avignon was the illness of the Pope, which retarded his decision on several important affairs. Clement VI. was fast approaching to his end, and Petrarch had little hope of his convalescence, at least in the hands of doctors. A message from the Pope produced an imprudent letter from the poet, in which he says, "Holy father! I shudder at the account of your fever; but, believe me, I am not a flatterer. I tremble to see your bed always surrounded with physicians, who are never agreed, because it would be a reproach to the second to think like the first. 'It is not to be doubted,' as Pliny says, 'that physicians, desiring to raise a name by their discoveries, make experiments upon us, and thus barter away our lives. There is no law for punishing their extreme ignorance. They learn their trade at our expense, they make some progress in the art of curing; and they alone are permitted to murder with impunity.' Holy father! consider as your enemies the crowd of physicians who beset you. It is in our age that we behold verified the prediction of the elder Cato, who declared that corruption would be general when the Greeks should have transmitted the sciences to Rome, and, above all, the science of healing. Whole nations have done without this art. The Roman republic, according to Pliny, was without physicians for six hundred years, and was never in a more flourishing condition."
The Pope, a poor dying old man, communicated Petrarch's letter immediately to his physicians, and it kindled in the whole faculty a flame of indignation, worthy of being described by Molière. Petrarch made a general enemy of the physicians, though, of course, the weakest and the worst of them were the first to attack him. One of them told him, "You are a foolhardy man, who, contemning the physicians, have no fear either of the fever or of the malaria." Petrarch replied, "I certainly have no assurance of being free from the attacks of either; but, if I were attacked by either, I should not think of calling in physicians."
His first assailant was one of Clement's own physicians, who loaded him with scurrility in a formal letter. These circumstances brought forth our poet's "Four Books of Invectives against Physicians," a work in which he undoubtedly exposes a great deal of contemporary quackery, but which, at the same time, scarcely leaves the physician-hunter on higher ground than his antagonists.