The third of the four causes, which cause is based on the nature of the simple: let this be realized from eight circumstances. First of these circumstances: offensiveness of the medicine. Second: lowering of its potency. Third: to correct its harmful effect. Fourth: to strengthen its virtue. Fifth: to lower or lessen its virulence. Sixth: to preserve its own quality. Seventh: the variability of the items by which the action is accomplished. Eighth: the lack of comfort afforded by the simple itself.