The first phase of feeling which Herder considers is _Reiz_ or stimulus. The peculiar phenomenon of stimulus says he, which may be seen in the smallest, most delicate filaments of plants, causing them to contract and expand, and bespeaking a sort of feeling is due to the same law which controls the most complicated feelings and passions of the human being. This all-pervading law of stimulus Herder finds in the action of physical heat and cold, which he makes parallel in its working with pleasure and pain respectively. Pain, disturbance by something foreign, contracts; the strength collects, increases for resistance, and takes its stand again. Well-being and pleasure—warmth—expands, makes for calmness, placidity, enjoyment, and release. That which is expansion and contraction in dead nature, the result of warmth and cold, seems to be here the obscure seed of stimulus and feeling in man. The “world-all,” the entire feeling, nature of human beings and animals moves in this ebb and flood of warmth and cold. The power to expand and contract which is the effect of this heat and cold, pleasure and pain, Herder makes the fundamental principle of the power for self-nutriment. This power is nothing external or mechanical, in which case it would not be life. The plant structure of organic fibers which takes in life from the surrounding elements does so through its own activities. The power to escape its enemies and to make over all its nourishment into differentiated parts lies within the plant. The complicated body of the animal likewise has this stimulus to seek the nutrition essential for life within: hunger and thirst are powerful exciting forces. When he applies his theories to man, he calls love the most powerful stimulus to life. Herder ascribes to the plant something in addition to the stimulus to seek nutrition when he recognizes that intelligence in plant structures which selects only such elements as fit the peculiar needs for its development after its kind. He does not succeed in getting rid entirely of the external in operating the organism; he sees in breathing a kind of time-beating by which nature swings the machine, and here nature is without, for she breathes upon the machine, in this harmonious way, the spirit of life. Thus far Herder has recognized the existence of a stimulus in the vegetable and animal kingdoms, which is in reality a life-principle. This life-principle is not only the monitor over the feelings, but merges into them and becomes the stuff of which feelings are made.