Through the midst of these variously erroneous theories, that traverse the field of thought in all directions, runs a tiny rivulet of golden truth. Starting from the subtle empiricism of Aristotle, it flows in the profound penetration of Vico to the nineteenth century, where it appears again in the masterly analyses of Schleiermacher, Humboldt, and De Sanctis. This brief list shows that the science of Aesthetic is no longer to be discovered, but it also shows _that it is only at its beginning_. The birth of a science is like the birth of a human being. In order to live, a science, like a man, has to withstand a thousand attacks of all sorts. These appear in the form of errors, which must be extirpated, if the science is not to perish. And when one set has been weeded, another crops up; when these have been dealt with, the former errors often return. Therefore _scientific criticism_ is always necessary. No science can repose on its laurels, complete, unchallenged. Like a human being, it must maintain its position by constant efforts, constant victories over error. The general errors which reveal a negation of the very concept of art have already been dealt with in the Historical Summary. The particular errors have been exposed in the Theory. They may be divided under three heads: (i.) Errors as to the characteristic quality of the aesthetic fact, or (ii.) as to its specific quality, or (iii.) as to its generic quality. These are contradictions of the characteristics of intuition, of theoretic contemplation, and of spiritual activity, which constitute the aesthetic fact. The principal bar to a proper understanding of the true nature of language has been and still is Rhetoric, with the modern form it has assumed, as style. The rhetorical categories are still mentioned in treatises and often referred to, as having definite existence among the parts of speech. Side by side with such phrases goes that of the double form, or metaphor, which implies that there are two ways of saying the same thing, the one simple, the other ornate. Kant, Herbart, Hegel, and many minor personages, have been shown to be victims of the rhetorical categories, and in our own day we have writers in Italy and in Germany who devote much attention to them, such as R. Bonghi and G. Gröber; the latter employs a phraseology which he borrows from the modern schools of psychology, but this does not alter the true nature of his argument. De Sanctis gave perhaps the clearest and most stimulating advice in his lectures on Rhetoric, which he termed Anti-rhetoric.