The three years which have elapsed since the publication of the first edition of this work have been years of great activity of thought on many of the subjects treated therein. Some changes and additions seemed therefore imperatively called for.

For example: There has sprung up recently among the foremost writers on evolution a warm discussion on the factors of evolution, their number and relative importance. I have therefore added a chapter (Chap. III, Part II) on this subject—not, indeed, to discuss it fully (for this would be impossible in the limits of a chapter), but to put the mind of the reader in position to understand it and to judge for himself.

Again: Every reader of the first edition must have remarked that there are many fundamental religious questions which I have not touched at all in Part III. I had avoided these because my own mind was not yet fully clear. I regarded what I then wrote as only a little leaven in a very large lump. I was willing to wait and let it work. In the mean time it has worked in my own mind, and I hope in the minds of others. I have therefore added two chapters to this part. In one I simply carry out to their logical consequences the doctrine of the Divine Immanency.