The second and more important volume of Romanes's work treats of "Mental evolution in man and the origin of human faculties." The distinguished psychologist gives a convincing proof in it "that the psychological barrier between man and the brute has been overcome." Man's power of conceptual thought and of abstraction has been gradually evolved from the non-conceptual stages of thought and ideation in the nearest related mammals. Man's highest mental powers--reason, speech, and conscience--have arisen from the lower stages of the same faculties in our primate ancestors (the simiæ and prosimiæ). Man has no single mental faculty which is his exclusive prerogative. His whole psychic life differs from that of the nearest related mammals only in degree, and not in kind; quantitatively, not qualitatively. I recommend those of my readers who are interested in these momentous questions of psychology to study the profound work of Romanes. I am completely at one with him and Darwin in almost all their views and convictions. Wherever an apparent discrepancy is found between these authors and my earlier productions, it is either a case of imperfect expression on my part or an unimportant difference in application of principle. For the rest, it is characteristic of this "science of ideas" that the most eminent philosophers hold entirely antagonistic views on its fundamental notions. CHAPTER VII PSYCHIC GRADATIONS Psychological Unity of Organic Nature--Material Basis of the Soul: Psychoplasm--Scale of Sensation--Scale of Movement--Scale of Reflex Action--Simple and Compound Reflex Action--Reflex Action and Consciousness--Scale of Perception--Unconscious and Conscious Perception--Scale of Memory--Unconscious and Conscious Memory--Association of Perceptions--Instinct--Primary and Secondary Instincts--Scale of Reason--Language--Emotion and Passion--The Will--Freedom of the Will