A breathtaking passage from Will Durant's Fallen Leaves: Last Words on Life, Love, War, and God:
See him, the newborn, dirty but marvelous, ridiculous in actuality, infinite in possibility, capable of that ultimate miracle— growth. Can you conceive it— that this queer bundle of sound and pain will come to know love, anxiety, prayer, suffering, creation, metaphysics, death? He cries; he has been so long asleep in the quiet warm womb of his mother; now suddenly he is compelled to breathe, and it hurts; compelled to see light, and it pierces him; compelled to hear noise, and it terrifies him. Cold strikes his skin, and he seems to be all pain. But it is not so; nature protects him against this initial onslaught of the world by dressing him in a general insensitivity. He sees the light only dimly; he hears the sounds as muffled and afar. For the most part he sleeps. His mother calls him a “little monkey,” and she is right; until he walks he will be like an ape, and even less of a biped, the womb-life having given his funny little legs the incalculable flexibility of a frog’s. Not till he talks will he leave the ape behind, and begin to climb precariously to the stature of a human being.
Watch him, and see how, bit by bit, he learns the nature of things by random movements of exploration. The world is a puzzle to him; and these haphazard responses of grasping, biting, and throwing are the pseudopodia, which he puts out to a perilous experience. Curiosity consumes and develops him; he would touch and taste everything from his rattle to the moon. For the rest he learns by imitation, though his parents think he learns by sermons. They teach him gentleness, and beat him; they teach him mildness of speech, and shout at him; they teach him a Stoic apathy to finance, and quarrel before him about the division of their income; they teach him honesty, and answer his most profound questions with lies. Our children bring us up by showing us, through imitation, what we really are.
Life is that which is discontent, which struggles and seeks, which suffers and creates. No mechanistic or materialistic philosophy can do it justice, or understand the silent growth and majesty of a tree, or compass the longing and laughter of children. Childhood may be defined as the age of play; therefore some children are never young, and some adults are never old.