{120} The second case, the inequality of the same person's progress in different subjects, may be looked at in another way. We may view it as incident to the better or worse quality, for all purposes, of the special organs concerned. Thus to take musical acquisition. This is commonly attributed to a good ear, meaning a delicate sense of musical notes, as shown in their nice discrimination. Discriminating is a different function from remembering; yet, we can only doubt that the fact of being able to discriminate acutely is accompanied by the power of remembering or retaining the impressions of the sense. The superiority of endowment that shows itself in the one function, embraces also the other. Hence we are entitled to say that the special retentiveness for any one subject, or department of training, varies with the local endowment involved: which is not to maintain an identical proposition, for the local endowment may be held as tested by delicacy of discrimination, a distinct fact from memory. Thus, a delicate sense of shades of colour would entail a good visual memory for spectacle; a delicate ear for articulation would indicate a memory for shades and varieties of pronunciation, thereby counting as a part of the verbal memory. So, delicate discrimination in the tactile muscles would be followed by rapid acquirements in manipulative or manual art. _The Ultimate Analysis of the Laws of Association_.--It is easy to reduce all the laws ever assigned, as governing the reproduction of our ideas, to three, Contiguity, Similarity, and Contrast. It is open to question whether these can be resolved any farther. The author has endeavoured to reduce Similarity to Contiguity, but his reasons show that he had not deeply considered the workings of similarity. Hamilton's criticisms on the attempt (Reid, p. 914) are just and irrefragable. By far the most important examples of the working of similarity are such as, by their very nature, preclude a former contiguity: as, for example, Franklin's identification of Electricity and lightning.