Of course these observations are general, for there arises the question, to what extent can the senses and imagination be trained? We may well conceive that there is a limit to the development of the sense organs. There must come a period when the optic or aural nerves can be attuned no further; and is the limit equal in all persons? The probability is that it is not. The physical character of the nerves almost certainly varies in different persons, some being able to appreciate more complex harmonies than others, granted the limit of development. This is a point which has to be considered, particularly in the case of music wherein as a rule, the higher the beauty the more complex the combinations of signs. There is a parallel problem to solve in respect of the imagination. We can well believe that there was something abnormal in the imagination of Shakespeare, beyond the probability that in his case the physiological system controlling the seat of the imagination was unusually advanced at birth. It is quite certain that with such a man a given training would result in a far greater advance in the functioning capacity of the imagination, than in the vast majority of persons who might commence the training on apparently equal terms; and he would be able to go further--to surpass the point which might be the limit of development with most persons. These questions are of the highest importance, but they cannot be determined. We are acquainted with certain facts relating to the general development of the sense organs, and of the imagination; and in regard to the former we know that there is a limit within comprehensible bounds, but we see only very dimly anything finite in the scope of the imagination. With what other term than "limitless" can we describe the imagination of a Shakespeare? But in all cases, whatever the natural conditions at birth, it is clear that hard work is the key to success in art, and though some must work harder than others to arrive at an equal result, it is satisfactory to know that generally Carlyle was right when he described "genius" as the transcendent capacity for taking trouble, and we are not surprised that Cicero should have come to the conclusion that diligence is a virtue that seems to include all the others.