Book 2
12
The true reason of this none but the gods indeed can truly understand, but men may know the probable cause. In a word, it is such as this; any part which is very compact is insensible to the touch or to a wound, and hence it is not painful to the touch or to a wound. For pain consists in an exasperated sense, but what is compact cannot be exasperated, and hence is not susceptible of pain. But a spongy part is very sensible, and is exasperated by an injury. But since dense parts also live by their innate heat, and possess sensibility by this heat, if then the exciting cause be material, such as either a sword, or a stone, the material part of the patient is not pained, for it is dense by nature. But if an intemperament of the innate heat seize it, there arises a change of the sense; the heat therefore is pained by itself, being roused within by the impression on the sense. The pains then are from nature’s being increased, or a redundance thereof.
