Souls therefore are the rays of this Sun, which is called in Sanskrit Brahma, and the nature of the ray is to extend and withdraw, to appear and disappear, and the duration of its existence is incomparably short when compared with the duration of the eternal God, the divine Spirit. There are living creatures, small germs, worms and insects who live no longer than a moment; and there are other beings whose life is a hundred years; and some live longer still; and yet even if it were a thousand years it is a moment compared with eternity. Time, as man knows it, is in the first place discerned by the knowledge of his own physical constitution.