ISABNORMAL (or Isanomalous) LINES, in physical geography, lines upon a map or chart connecting places having an abnormal temperature. Each place has, theoretically, a proper temperature due to its latitude, and modified by its configuration. Its mean temperature for a particular period is decided by observation and called its normal temperature. Isabnormal lines may be used to denote the variations due to warm winds or currents, great altitudes or depressions, or great land masses as compared with sea. Or they may be used to indicate the abnormal result of weather observations made in an area such as the British Isles for a particular period.
ISAEUS (c. 420 B.C.-c. 350 B.C.), Attic orator, the chronological limits of whose extant work fall between the years 390 and 353 B.C., is described in the Plutarchic life as a Chalcidian; by Suidas, whom Dionysius follows, as an Athenian. The accounts have been reconciled by supposing that his family sprang from the settlement (κληρουχία) of Athenian citizens among whom the lands of the Chalcidian hippobotae (knights) had been divided about 509 B.C. In 411 B.C. Euboea (except Oreos) revolted from Athens; and it would not have been strange if residents of Athenian origin had then migrated from the hostile island to Attica. Such a connexion with Euboea would explain the non-Athenian name Diagoras which is borne by the father of Isaeus, while the latter is said to have been “an Athenian by descent” (Ἀθηναῖος τὸ γένος). So far as we know, Isaeus took no part in the public affairs of Athens. “I cannot tell,” says Dionysius, “what were the politics of Isaeus—or whether he had any politics at all.” Those words strikingly attest the profound change which was passing over the life of the Greek cities. It would have been scarcely possible, fifty years earlier, that an eminent Athenian with the powers of Isaeus should have failed to leave on record some proof of his interest in the political concerns of Athens or of Greece. But now, with the decline of personal devotion to the state, the life of an active citizen had ceased to have any necessary contact with political affairs. Already we are at the beginning of that transition which is to lead from the old life of Hellenic citizenship to that Hellenism whose children are citizens of the world.
Isaeus (who was born probably about 420 B.C.) is believed to have been an early pupil of Isocrates, and he certainly was a student of Lysias. A passage of Photius has been understood as meaning that personal relations had existed between Isaeus and Plato, but this view appears erroneous.[1] The profession of Isaeus was that of which Antiphon had been the first representative at Athens—that of a λογογράφος, who composed speeches which his clients were to deliver in the law-courts. But, while Antiphon had written such speeches chiefly (as Lysias frequently) for public causes, it was with private causes that Isaeus was almost exclusively concerned. The fact marks the progressive subdivision of labour in his calling, and the extent to which the smaller interests of private life now absorbed the attention of the citizen.
The most interesting recorded event in the career of Isaeus is one which belongs to its middle period—his connexion with Demosthenes. Born in 384 B.C., Demosthenes attained his civic majority in 366. At this time he had already resolved to prosecute the fraudulent guardians who had stripped him of his patrimony. In prospect of such a legal contest, he could have found no better ally than Isaeus. That the young Demosthenes actually resorted to his aid is beyond reasonable doubt. But the pseudo-Plutarch embellishes the story after his fashion. He says that Demosthenes, on coming of age, took Isaeus into his house, and studied with him for four years—paying him the sum of 10,000 drachmas (about £400), on condition that Isaeus should withdraw from a school of rhetoric which he had opened, and devote himself wholly to his new pupil. The real Plutarch gives us a more sober and a more probable version. He simply states that Demosthenes “employed Isaeus as his master in rhetoric, though Isocrates was then teaching, either (as some say) because he could not pay Isocrates the prescribed fee of ten minae, or because he preferred the style of Isaeus for his purpose, as being vigorous and astute” (δραστήριον καὶ πανοῦργον). It may be observed that, except by the pseudo-Plutarch, a school of Isaeus is not mentioned,—for a notice in Plutarch need mean no more than that he had written a textbook, or that his speeches were read in schools;[2] nor is any other pupil named. As to Demosthenes, his own speeches against Aphobus and Onetor (363-362 B.C.) afford the best possible gauge of the sense and the measure in which he was the disciple of Isaeus; the intercourse between them can scarcely have been either very close or very long. The date at which Isaeus died can only be conjectured from his work; it may be placed about 350 B.C.
Isaeus has a double claim on the student of Greek literature. He is the first Greek writer who comes before us as a consummate master of strict forensic controversy. He also holds a most important place in the general development of practical oratory, and therefore in the history of Attic prose. Antiphon marks the beginning of that development, Demosthenes its consummation. Between them stand Lysias and Isaeus. The open, even ostentatious, art of Antiphon had been austere and rigid. The concealed art of Lysias had charmed and persuaded by a versatile semblance of natural grace and simplicity. Isaeus brings us to a final stage of transition, in which the gifts distinctive of Lysias were to be fused into a perfect harmony with that masterly art which receives its most powerful expression in Demosthenes. Here, then, are the two cardinal points by which the place of Isaeus must be determined. We must consider, first, his relation to Lysias; secondly, his relation to Demosthenes.
A comparison of Isaeus and Lysias must set out from the distinction between choice of words (λέξις) and mode of putting words together (σύνθεσις). In choice of words, diction, Lysias and Isaeus are closely alike. Both are clear, pure, simple, concise; both have the stamp of persuasive plainness (ἀφέλεια), and both combine it with graphic power (ἐνάργεια). In mode of putting words together, composition, there is, however a striking difference. Lysias threw off the stiff restraints of the earlier periodic style, with its wooden monotony; he is too fond indeed of antithesis always to avoid a rigid effect; but, on the whole, his style is easy, flexible and various; above all, its subtle art usually succeeds in appearing natural. Now this is just what the art of Isaeus does not achieve. With less love of antithesis than Lysias, and with a diction almost equally pure and plain, he yet habitually conveys the impression of conscious and confident art. Hence he is least effective in adapting his style to those characters in which Lysias peculiarly excelled—the ingenuous youth, the homely and peace-loving citizen. On the other hand, his more open and vigorous art does not interfere with his moral persuasiveness where there is scope for reasoned remonstrance, for keen argument or for powerful denunciation. Passing from the formal to the real side of his work, from diction and composition to the treatment of subject-matter, we find the divergence wider still. Lysias usually adheres to a simple four-fold division—proem, narrative, proof, epilogue. Isaeus frequently interweaves the narrative with the proof.[3] He shows the most dexterous ingenuity in adapting his manifold tactics to the case in hand, and often “out-generals” (καταστρατηγεῖ) his adversary by some novel and daring disposition of his forces. Lysias, again, usually contents himself with a merely rhetorical or sketchy proof; Isaeus aims at strict logical demonstration, worked out through all its steps. As Sir William Jones well remarks, Isaeus lays close siege to the understandings of the jury.[4]
Such is the general relation of Isaeus to Lysias. What, we must next ask, is the relation of Isaeus to Demosthenes? The Greek critic who had so carefully studied both authors states his own view in broad terms when he declares that “the power of Demosthenes took its seeds and its beginnings from Isaeus” (Dion. Halic. Isaeus, 20). A closer examination will show that within certain limits the statement may be allowed. Attic prose expression had been continuously developed as an art; the true link between Isaeus and Demosthenes is technical, depending on their continuity. Isaeus had made some original contributions to the resources of the art; and Demosthenes had not failed to profit by these. The composition of Demosthenes resembles that of Isaeus in blending terse and vigorous periods with passages of more lax and fluent ease, as well as in that dramatic vivacity which is given by rhetorical question and similar devices. In the versatile disposition of subject-matter, the divisions of “narrative” and “proof” being shifted and interwoven according to circumstances, Demosthenes has clearly been instructed by the example of Isaeus. Still more plainly and strikingly is this so in regard to the elaboration of systematic, proof; here Demosthenes invites direct and close comparison with Isaeus by his method of drawing out a chain of arguments, or enforcing a proposition by strict legal argument. And, more generally, Demosthenes is the pupil of Isaeus, though here the pupil became even greater than the master, in that faculty of grappling with an adversary’s case point by point, in that aptitude for close and strenuous conflict which is expressed by the words ἀγών, ἐναγώνιος.[5]
The pseudo-Plutarch, in his life of Isaeus, mentions an Art of Rhetoric and sixty-four speeches, of which fifty were accounted genuine. From a passage of Photius it appears that at least[6] the fifty speeches of recognized authenticity were extant as late as A.D. 850. Only eleven, with a large part of a twelfth, have come down to us; but the titles of forty-two[7] others are known.[8]