Man is as much attached to nature as a tree, and though he walks freely on two legs and is not rooted in the soil, he is by no means a self-sufficient, self-moving, and self-directing entity. For his life he depends absolutely on the same factors as the tree, the worm, and the fly, on the universal powers of nature, life, God, or whatever it may be. From some mysterious source life flows through him unceasingly; it does not just go in at birth and come out at death—he is the channel for an ever moving stream, a stream that carries the blood through his veins, that moves his lungs and brings him air to breathe, that raises his food from the earth and bears the light of the sun to his face. If we look into a single cell of his body we find the universe, for sun, moon, and stars are ceaselessly maintaining it; we find it again if we plumb into the depths of his mind, for there are all the archaic urges of primeval life, both human and animal, and could we look deeper we might find kinship with the plants and rocks. [...]
The isolation of the human soul from nature is, generally speaking, a phenomenon of civilization. This isolation is more apparent than real, because the more nature is held back by brick, concrete, and machines, the more it reasserts itself in the human mind, usually as an unwanted, violent, and troublesome visitor. But actually the creations of man, his art, his literature, his buildings, differ only in quality, not in kind, from such creations of nature as birds’ nests and honeycombs. Man’s creations are infinitely more numerous and ingenious, but this very ingenuity, together with his fear, aggravates his feeling of isolation, persuading him that he is a creator in his own right, separate from nature. For once again it would go against his self-esteem to have to admit that his superb faculty of reason and all its works do not make him the master of nature rather than its servant. Bewitched by his power of reason and urged on through fright of his fear, man seeks his freedom in isolation from and not in union with nature—“whose service is perfect freedom.” [...]
Man’s struggle for mastery is magnificent and tragic; but it does not work. And the difficulty is not so much in what he does as in what he thinks. If he were to seek union instead of isolation this would not involve what is generally called “getting back to nature”; he would not have to give up his machines and cities and retire to the forests and live in wigwams. He would only have to change his attitude, for the penalties he pays for his isolation are only indirectly on the physical plane. They originate from and are most severe in his mind.
From "The Meaning of Happiness: The Quest for Freedom of the Spirit in Modern Psychology and the Wisdom of the East."