ABSTRACT
§ 117. On considering after what manner we habitually distinguish between a live object and a dead one, we shall find that we do so by observing whether a change which we make in the surrounding conditions, or one which Nature makes in them, is or is not followed by some perceptible change in the object. By discovering that certain things shrink when touched, or fly away when approached, or start when a noise is made, the child first roughly discriminates between the living and the not living; and the man when in doubt whether an animal he is looking at is dead or not, stirs it with his stick; or if it be at a distance, shouts, or throws a stone at it. Vegetable and animal life are alike primarily recognized by this process. The tree that puts out leaves when the spring brings a change of temperature; the flower which opens and closes with the rising and setting of the sun; the plant that droops when the soil is dry, and re-erects itself when watered; are considered alive in virtue of these induced changes: in common with the zoophyte which contracts on the passing of a cloud over the sun; the worm that comes out on to the surface when the ground is continuously shaken; and the hedgehog that rolls itself up when attacked.
