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...deviate, so much so that it becomes necessary to leave the primary disease aside and heal the accidents original: "accidentibus"; in Galenic medicine, these are the secondary symptoms or complications that arise from a disease by administering contrary remedies. The Physician must take care that, by neglecting these symptoms, he does not lead the patient into the greatest risk to life and total ruin. For this reason, symptoms are not to be overlooked; Galen Galen of Pergamon (129–c. 216 AD), the most influential Greek physician in the Roman Empire alludes to this same opinion in the twelfth book of his Method of Healing, saying that powerful symptoms can overthrow the vitality original: "uirtutem" (virtus); the innate power or "life force" of the body to heal itself and maintain function. He taught how to assist them in the eighth commentary on the first part of the Aphorisms, ordering that food be offered immediately if the vitality should fail. Avicenna The Latinized name of Ibn Sina, whose work formed the backbone of medieval university medicine, moved by similar reasoning, stated in the fourth [chapter] of the first [book]: "it is proper to focus on the matter that is most suspect," and that is the vitality. For if you do not oppose the symptoms that overthrow the vitality—for example, extreme insomnia original: "uigiliis" and headaches during a fever—there is a danger that these may increase the fever or produce a worse disease, such as phrenitis a condition of delirium or brain inflammation believed to be caused by yellow bile arising from excessive wakefulness and headache.

And, because we can hardly recognize abnormal conditions except by knowing the natural disposition of the same kind (by way of contrast), therefore, in the fourth place,
Temperament. it is necessary to understand the temperament original: "temperaturam"; the specific balance of the four qualities—heat, cold, moisture, and dryness—unique to an individual, so that through it you may recognize the disease of that kind. Once this is perceived and compared with the natural balance, you will be able to know whether the illness is greater or lesser, as you find throughout the volumes of Galen, and especially at the beginning of the first book of the Art of Healing, dedicated to Glaucon, where he says: "to the extent we see someone has distanced themselves from their natural state, to that extent we shall judge the magnitude of their disease." Avicenna also mentions this in the fourth [chapter] of the first [book]. Therefore, you shall investigate the temperament of the sick so that you may know whether they have contracted an equal temperament according to "justice" original: "secundum iustitiam"; referring to a state of perfect humoral equilibrium, or whether heat, cold, moisture, or dryness predominates. For thus (as I said a little before), you will recognize the magnitude of the disease by its distance from the patient’s own temperament.

Vitality. To this record, you shall fifthly add the knowledge of Vitality; for vitality and temperament agree in some ways, even if they differ in others. According to the opinion of Averroes Ibn Rushd (1126–1198), an Andalusian philosopher and physician known for his commentaries on Aristotle and Galen in the ninth chapter of the first [book], you will gather that they act as the primary and the instrumental forces. You shall investigate with the greatest diligence what kind of vitality the patient possesses. For as Galen said in the eleventh book of his Method, vitality is the opponent of disease, like a strong warrior; and in another place he said that the Physician ought to direct his right eye toward the vitality and his left eye toward the sickness. And Avicenna, in the first [chapter] of the fourth [book] on the cure of fevers in general, said it is necessary in all things to [evaluate] the vitality...