This is the only metrical rule which Demosthenes ever observed, and one of the soundest of modern critics believes that even this observance was instinctive rather than conscious.[358] He never affected any metrical formula for the end of sentences comparable to Cicero’s famous _esse videatur_, or the double trochee –⏑–⏑ at the beginning of a sentence, approved by later writers. An examination shows that he has an almost infinite variety both in the opening and the close of his sentences. He seems never to follow any mechanical system. Much labour has been expended, especially in Germany, on the analysis of the rhythmical element in Demosthenes’ style. There is no doubt that many orators, from Gorgias onwards, laboured to produce approximate correspondence between parallel or contrasted sections of their periods. In some cases we find an equal number of syllables in two clauses, and even a more or less complete rhythmical correspondence. Such devices serve to emphasize the peculiar figures of speech in which Gorgias delighted, and may have been appropriate to the class of oratory intended primarily for display, but it is hard to believe that such elaboration was ever consciously carried through a long forensic speech. The appendix to the third volume of Blass’ Attic oratory is a monumental piece of work. It consists of an analysis of the first seventeen sections of the _de Corona_, and the whole of the _First Olynthiac_ and _Third Philippic_ speeches, and conveys the impression that this Demosthenic prose may be scanned with almost as much certainty as a comparatively simple form of composition like a Pindaric ode. It is hard to pronounce on such a matter without a very long and careful study of this difficult subject; but the theory of rhythmical correspondence seems to have been worked out far too minutely. In many cases emendation is required; we have to divide words in the middle, and clauses are split up in an arbitrary and unnatural way. I am far from believing that analysis can justifiably be carried to this extent; it is more reasonable to suppose that Demosthenes had a naturally acute ear, and that practice so developed his faculty that a certain rhythm was natural to all his speech. I am not convinced that all his effects were designed.[359] § 6. _Rhetorical Devices_ Isaeus, the teacher of Demosthenes, was a master of reasoning and demonstration; Demosthenes in his earliest speeches shows strong traces of the influence of Isaeus, but in his later work he has developed varied gifts which enable him to surpass his master. Realizing the insufficiency, for a popular audience, of mere reasoning, he reinforced his logic by adventitious aids, appealing in numerous indirect ways to feeling and prejudice. One valuable method of awakening interest was his striking use of paradox: