Beyond these sections, there are classes of pictures which do not belong to the pure art of the painter, namely, those executed for use and not for beauty[35]; those painted to illustrate sports, or to record passing events; certain allegorical paintings; and those works which, while they cannot represent the ideal, require the assistance of another art for their interpretation; as for instance, incidents to illustrate particular morals or stories; scenes from the drama other than tragedy; portraits of persons in character; humorous subjects, and so on. Such works, on account of the restrictions imposed on the artist, can exhibit but limited and fleeting beauty. Elsewhere they are noticed under the heading of "Secondary Art." CHAPTER VI EXPRESSION. PART I.--THE IDEAL The human being is the only sign in the arts capable of idealization, because, while its parts are fixed and invariable, it is the only sign as to which there is a universal agreement in respect of the value of abstract qualities connected with it. There can be no ideal of the human form separately, because this implies expression which results from abstract qualities. Nor can there be an ideal combination of these qualities, except a general expression covering all the virtues and eliminating all the passions, which expression cannot be disassociated from form. The ideal human being is therefore a perfect generalization of the highest conceivable qualities of form and expression. Necessarily in matters of art, when we use the term "Ideal," we mean a general ideal, that is to say, an ideal that would be accepted as such by the general body of men and women. From the fact that the sensorial nerves in all persons are alike in form and character, and that they act in the same way under like conditions, it follows that there must be a general agreement as to degrees of beauty, and thus a common conception of the ideal human being. Experience has demonstrated this at all times, both in respect of the general ideal we are now discussing, and of particular ideals involving special types and characters; and so invariable is this experience that the progression towards similar ideals has all the force of law.[36] This general agreement is subject to certain restrictions. The first is in regard to form in which the imagination cannot proceed beyond experience. The component parts of an ideal form cannot include any which are higher in quality than those which have come within the experience of the person compounding the ideal. Secondly, in regard to abstract qualities, the estimation of these depends upon intelligence and education, and the accumulated experience of these things, which we measure in terms of degrees of civilization. Consequently, different interpretations would be placed upon the phrase "the highest conceivable qualities of form and expression," by the various races of mankind. According as the experience was greater, so would the ideal form be higher in type; and