Any theory of pleasure-pain then from the point of view of pure psychology, as explaining it by reference to other modes of consciousness, is, we think, unsatisfactory. But perhaps the physiological point of view will be more satisfactory. It is generally considered that the function and origin of pain is in what is unfavourable to physiological function, of pleasure, in what is favourable. I cut my finger, and the pain says, stop the injurious action. However, there are exceptions. I taste sugar of lead; it is pleasant, and I keep on tasting, and am poisoned. Lotze explains that this sweetness is immediately soothing and advantageous. “We must not regard pleasure,” says Grant Allen, as “prophetic.” But what has been the evolution of taste as sensing act except to be “prophetic,” to give at the opening of the alimentary canal a monitor to the stomach and other digestive organs? That it tastes sweet, that this taste is pleasant, and so the substance is swallowed, or that it tastes bitter and unpleasant, and the substance is rejected; this surely is anticipatory and “prophetic.” The taste for sweetness is not evolved for itself; but for its life value; and hence Lotze’s explanation fails from the point of view of evolutionary psychology. The organic sweet is the nutritious and beneficial, and the sensing this quality in connection with these favourable and pleasant effects on the stomach and organism as a whole has led to a taste and liking for sweetness. “Sweet and wholesome” is the common and just conception. But if mineral sweets injurious to life, like sugar of lead, had been a common environment, and the only sweet known, this sweetness would have been as unpleasant as the sour or acid now is. We see even now that sweets that have several times caused nausea, though at first highly agreeable, come to be distasteful and disgustful. We now find that sour and bitter substances are disliked by animals in general as painful, for the sour and bitter is general sign of the unwholesome; but those animals which live almost exclusively on bitter herbs undoubtedly appreciate this quality as we do a _bon bon_. Men lost in a desert by pertinaciously tasting bitter herbs and becoming dependent upon them for support would soon realize their bitterness as pleasant, and a race might originate to whom sweetness would be unpleasant. Hence the value of a sensation does not—in natural evolution—lie in itself, it is merely a guide and index; and the sensation quality will be pleasant or unpleasant according to its relation to the demands of life. A sensation is inherently either pleasurable or painful, but not essentially one and not the other, hence the proverb, _de gustibus non disputandum_. The sensing act in itself is indifferent, _i.e._, sweetness and bitterness, purely as tastes, as sensing acts, are indifferent; but as matter of fact having grown up with and for pleasure-pain tones as indicative of life values, they are