The Fourth Trope. This Trope limits the argument to each separate sense, and the effect is considered of the condition of body and mind upon sense-perception in relation to the several sense-organs.[1] The physical states which modify sense-perception are health and illness, sleeping and waking, youth and age, hunger and satiety, drunkenness and sobriety. All of these conditions of the body entirely change the character of the mental images, producing different judgments of the color, taste, and temperature of objects, and of the character of sounds. A man who is asleep is in a different world from one awake, the existence of both worlds being relative to the condition of waking and sleeping.[2]
The subjective states which Sextus mentions here as modifying the character of the mental representations are hating or loving, courage or fear, sorrow or joy, and sanity or insanity.[3] No man is ever twice in exactly the same condition of body or mind, and never able to review the differences of his ideas as a sum total, for those of the present moment only are subject to careful inspection.[4] Furthermore, no one is free from the influence of all conditions of body or mind, so that he can be unbiassed to judge his ideas, and no criterion can be established that can be shown to be true, but on the contrary, whatever course is pursued on the subject, both the criterion and the proof will be thrown into the circulus in probando, for the truth of each rests on the other.[5]
[1] Hyp. I. 100.
[2] Hyp. I. 104.
[3] Hyp. I. 100.
[4] Hyp. I. 112.
[5] Hyp. I. 117.
Diogenes gives in part the same illustrations of this Trope, but in a much more condensed form. The marked characteristic of this train of reasoning is the attempt to prove that abnormal conditions are also natural. In referring at first to the opposing states of body and mind, which so change the character of sense-perception, Sextus classifies them according to the popular usage as κατὰ φύσιν and παρὰ φύσιν. This distinction was an important one, even with Aristotle, and was especially developed by the Stoics[1] in a broader sense than referring merely to health and sickness. The Stoics, however, considered only normal conditions as being according to nature. Sextus, on the contrary, declares that abnormal states are also conditions according to nature,[2] and just as those who are in health are in a state that is natural to those who are in health, so also those not in health are in a state that is natural to those not in health, and in some respects according to nature. Existence, then, and non-existence are not absolute, but relative, and the world of sleep as really exists for those who are asleep as the things that exist in waking exist, although they do not exist in sleep.[3] One mental representation, therefore, cannot be judged by another, which is also in a state of relation to existing physical and mental conditions. Diogenes states this principle even more decidedly in his exposition of this Trope. "The insane are not in a condition opposed to nature; why they more than we? For we also see the sun as if it were stationary."[4] Furthermore, in different periods of life ideas differ. Children are fond of balls and hoops, while those in their prime prefer other things, and the aged still others.[5] The wisdom contained in this Trope in reference to the relative value of the things most sought after is not original with Sextus, but is found in the more earnest ethical teachings of older writers. Sextus does not, however, draw any moral conclusions from this reasoning, but only uses it as an argument for ἐποχή.
[1] Diog. VII. 1, 86.
[2] Hyp. I. 103.