You must admit there are no definite external causes of pain nor those of pleasure, for one and the same thing causes pain at one time and pleasure at another. A cause of delight to one person turns out to be that of aversion to another. A dying miser might revive at the sight of gold, yet a Diogenes would pass without noticing it. Cigars and wine are blessed gifts of heaven to the intemperate,[FN#215] but accursed poison to the temperate. Some might enjoy a long life, but others would heartily desire to curtail it. Some might groan under a slight indisposition, while others would whistle away a life of serious disease. An Epicure might be taken prisoner by poverty, yet an Epictetus would fearlessly face and vanquish him. How, then, do you distinguish the real cause of pain from that of pleasure? How do you know the causes of one are more numerous than the causes of the other? [FN#215] The author of Han Shu (Kan Sho) calls spirits the gift of Heaven. Expose thermometers of several kinds to one and the same temperature. One will indicate, say, 60°, another as high as 100°, another as low as 15°. Expose the thermometers of human sensibilities, which are of myriads of different kinds, to one and the same temperature of environment. None of them will indicate the same degrees. In one and the same climate, which we think moderate, the Eskimo would be washed with perspiration, while the Hindu would shudder with cold. Similarly, under one and the same circumstance some might be extremely miserable and think it unbearable, yet others would be contented and happy. Therefore we may safely conclude that there are no definite external causes of pain and pleasure, and that there must be internal causes which modify the external. 3. The Law of Balance. Nature governs the world with her law of balance. She puts things ever in pairs,[FN#216] and leaves nothing in isolation. Positives stand in opposition to negatives, actives to passives, males to females, and so on. Thus we get the ebb in opposition to the flood tide; the centrifugal force to the centripetal; attraction to repulsion; growth to decay; toxin to antitoxin; light to shade; action to reaction; unity to variety; day to night; the animate to the inanimate. Look at our own bodies: the right eye is placed side by side with the left; the left shoulder with the right; the right lung with the left; the left hemisphere of the brain with that of the right; and so forth. [FN#216] Zenists call them 'pairs of opposites.'