The, necessity in art for the expression of value is, I think, the principal difference between art and science, rather than, as Croce [Footnote: _Estetica_, quarta edizione, p.27; English translation. p.36.] supposes, the limitation of art to the expression of the individual and of Science to the expression of the concept. For, on the one hand, science may express the individual; and, on the other hand, art may express the concept. The geographer, for example, describes and makes maps of particular regions of the earth's surface; the astronomer studies the individual sun and moon. Poets like Dante, Lucretius, Shakespeare, and Goethe express the most universal concepts of ethics or metaphysics. But what makes men poets rather than men of science is precisely that they never limit themselves to the mere clear statement of the concept, but always express its human significance as well. A theory of human destiny is expressed in Prospero's lines-- We are such stuff As dreams are made of, and our little life Is rounded with a sleep; but with overtones of feeling at the core. Or consider the passion with which Lucretius argues for a naturalistic conception of the universe. And the reason why poets clothe their philosophical expressions in concrete images is not because of any shame of the concept, but just in order the more easily and vividly to attach and communicate their emotion. Their general preference for the concrete has the same motive; for there are only a few abstractions capable of arousing and fixing emotion.