be considered as a reaction that takes place in response to the stimulus of the impression. Conception of course is also an active process, and concepts, the products of conception, establish a new department in the mind. "Noiré, quoted by Prof. Max Müller, says: 'All trees hitherto seen by me leave in my imagination a mixed image, a kind of ideal presentation of a tree. Quite different from this is my concept, which is never an image.'"[1]
And this is true.
We have on another occasion explained that sensations are sense-impressions which have acquired meaning.[2] Rays of light are reflected from an object and fall upon the retina of an eye. Here they produce a disturbance of nervous substance which is transmitted to the brain where it is felt as the image say of a tree. Now the ether-waves are not sight, but a certain form of ether-waves corresponds to a certain form of sight, and the latter comes to stand for the former. The mental picture of a tree becomes a symbol for a special object outside of us and it is projected to the place where experience has taught us to expect that object. In naming objects we repeat the process of expressing by symbols. Sensations are symbols, and names are symbols of symbols. The name and concept tree is not the composite picture of all the trees I have seen, but it is the symbol of this composite picture of sense-impressions. Sensations are like the chords of a piano and the concepts are like the keys. The key is different in kind from the chord which belongs to it. When I touch the key the chord will sound: when I pronounce a name the composite sensation of all its analogous memories will be awakened. *** Can there be any question that difference in kind can originate by degrees? Professor Romanes uses the phrase "different in kind" as synonymous with "different in origin" and therefore declares that human reason and animal intelligence are " different in degree"
