Again, on the physical plane we not only see men dwelling together in cities and villages, but even beasts and birds living in flocks and herds; coal is found in the coal-mine, and gold in the gold-mine, the forest contains thousands of trees, whereas the desert holds not a single one. All this proves the power of affinity which collects and groups the atoms of like kind and makes of them numerous forms, thereby creating an illusion before the eye of man who thus forgets the one source in the manifestation of variety.