But here let me interpose a word of caution. I must avoid the error which vitiates Professor Drummond’s interesting work on ‘Natural Law in the Spiritual World,’ of confounding analogy and identity. Because the principle of polarity pervades alike the natural and spiritual worlds, I am far from assuming that the laws under which it acts are identical; and that virtue and vice, pain and pleasure, ugliness and beauty, are products of the same mathematical changes of sign and inverse squares or cubes of distances, as regulate the attractions and repulsions of molecules and atoms. All I say is, that the same pervading principle may be traced wherever human thought and human knowledge extend; that it is apparently, for some reason unknown to us, the essential condition of all existence within the sphere of that thought and that knowledge; and that what lies beyond it is the great unknown, behind the impenetrable veil which it is not given to mortals to uplift. In like manner, if I call myself ‘a modern Zoroastrian,’ it is not that I wish or expect to teach a new religion or revive an old one, to see Christian churches dedicated to Ormuzd, or right reverend bishops exchanging the apron and shovel-hat for the mitre and flowing robes of the ancient Magi; but simply this. All religions I take to be ‘working hypotheses,’ by which successive ages and races of men try to satisfy the aspirations and harmonise the knowledge which in the course of evolution have come to be, for the time, their spiritual equipment. The best proof of any religion is, that it exists—i.e. that it is part of the same evolution, and that on the whole it works well, i.e. is in tolerable harmony with its environment. When that environment changes, when loftier views of morality prevail, when knowledge is increased and the domain of science everywhere extends its frontier, religions must change with it if they are to remain good working, and not become unworkable and unbelievable hypotheses. Now of all the religious hypotheses which remain workable in the present state of human knowledge, that seems to me the best which frankly recognises the existence of this dual law, or law of polarity, as the fundamental condition of the universe, and, personifying the good principle under the name of Ormuzd, and the evil one under that of Ahriman, looks with earnest but silent and unspoken reverence on the great unknown beyond, which may, in some way incomprehensible to mortals, reconcile the two opposites, and give the final victory to the good. Oh! yet we hope that somehow good Will be the final goal of ill. So sings the poet of the nineteenth century: so, if we understand his doctrine rightly, taught the Bactrian sage, Zoroaster, some forty centuries earlier.