The alchemists, I hold, convinced of the truth of this view of Nature, _i.e_. that principles true of one plane of being are true also of all other planes, adopted analogy as their guide in dealing with the facts of chemistry and physics known to them. They endeavoured to explain these facts by an application to them of the principles of mystical theology, their chief aim being to prove the truth of these principles as applied to the facts of the natural realm, and by studying natural phenomena to become instructed in spiritual truth. They did not proceed by the sure, but slow, method of modern science, _i.e_. the method of induction, which questions experience at every step in the construction of a theory; but they boldly allowed their imaginations to leap ahead and to formulate a complete theory of the Cosmos on the strength of but few facts. This led them into many fantastic errors, but I would not venture to deny them an intuitive perception of certain fundamental truths concerning the constitution of the Cosmos, even if they distorted these truths and dressed them in a fantastic garb. Now, as I hope to make plain in the course of this excursion, the alchemists regarded the discovery of the Philosopher's Stone and the transmutation of "base" metals into gold as the consummation of the proof of the doctrines of mystical theology as applied to chemical phenomena, and it was as such that they so ardently sought to achieve the _magnum opus_, as this transmutation was called. Of course, it would be useless to deny that many, accepting the truth of the great alchemical theorem, sought for the Philosopher's Stone because of what was claimed for it in the way of material benefits. But, as I have already indicated, with the nobler alchemists this was not the case, and the desire for wealth, if present at all, was merely a secondary object.