If we substitute for the word Pleasure the equivalent phrase--a feeling which we seek to bring into consciousness and retain there, and if we substitute for the word Pain the equivalent phrase--a feeling which we seek to get out of consciousness and to keep out; we see at once that if the states of consciousness which a creature endeavors to maintain are the correlatives of injurious actions, and if the states of consciousness which it endeavors to expel are the correlatives of beneficial actions, it must quickly disappear through persistence in the injurious, and avoidance of the beneficial. In other words, those races of beings only can have survived in which, on the average, agreeable or desired feelings went along with activities conducive to the maintenance of life, while disagreeable and habitually avoided feelings went along with activities directly or indirectly destructive of life; and there must ever have been, other things equal, the most numerous and long-continued survivals among races in which these adjustments of feelings to actions were the best, tending ever to bring about perfect adjustment. Fit connections between acts and results must establish themselves in living things, even before consciousness arises; and after the rise of consciousness these connections can change in no other way than to become better established. At the very outset, life is maintained by persistence in acts which conduce to it, and desistance from acts which impede it; and whenever sentiency make its appearance as an accompaniment, its forms must be such that in the one case the produced feeling is of a kind that will be sought--pleasure, and in the other case is of a kind that will be shunned--pain. Observe the necessity of these relations as exhibited in the concrete. A plant which envelops a buried bone with a plexus of rootlets, or a potato which directs its blanched shoots toward a grating through which light comes into the cellar, shows us that the changes which outer agents themselves set up in its tissues are changes which aid the utilization of these agents. If we ask what would happen if a plant's roots grew not toward the place where there was moisture, but away from it, or if its leaves, enabled by light to assimilate, nevertheless bent themselves toward the darkness, we see that death would result in the absence of the existing adjustments. This general relation is still better shown in an insectivorous plant, such as the _Dionoea muscipula_, which keeps its trap closed round animal matter, but not round other matter. Here it is manifest that the stimulus arising from the first part of the absorbed substance itself sets up those actions by which the mass of the substance is utilized for the plant's benefit.