Or take the _evolution series_ from protozoan to man. This we have already seen is similar in outline to the other two. Now, in the gradual evolution of the animal kingdom throughout all geological time, terminating in man, when did immortal spirit come in? Did it enter with life, or with sentient life, or somewhere in the ascending scale of animals, or with the advent of man? If with man, was it some new thing added at once out of hand, or did it grow out of something already existing in animals? This last, we are persuaded, is the only tenable view--the only view that can effect that reconciliation between the two extreme, mutually excluding views now usually held, which, as already seen, is the true test of a rational philosophy. I believe that the spirit of man _was_ developed out of the _anima_ or conscious principle of animals, and that this, again, was developed out of the lower forms of life-force, and this in its turn out of the chemical and physical forces of Nature; and that at a certain stage in this gradual development, viz., with man, it _acquired_ the property of immortality precisely as it now, in the individual history of each man at a certain stage, acquires the capacity of abstract thought. This is, in brief, the view which I wish to enforce. The reader must understand, however, that this is _my own view_ only, a view for which I have earnestly contended for twenty years. It appeals, therefore, not to authority, but only to reason. I wish now to present it as briefly as possible.