The following excerpt from Homer and His Poems, by N. M. Cohen summarizes nicely the background to Lachmann's theory regarding the Illiad:
"The first study of Homer that can really be called critical was made in the Alexandrian Age. Then arose a school of Separatists (about 170 B. C.) who believed that the Iliad and the Odyssey were by different authors. Zenodotus, the first chief of the great museum, was also the first critic of the Homeric text, and he was soon followed by Aristarchus, the greatest of ancient critics, to whom is ascribed the present division of Homer into books. Aristarchus discovered a number of spurious passages in the poems, but he had no doubt that Homer was virtually their author.
At the end of the 18th century there was found in Venice, in the library of St. Mark, a manuscript of the Iliad, dating from the 10th century. Around this transcription were marginal notes, called "scholia." These were textual criticisms by Aristarchus and other learned grammarians. The finding of the "scholia" gave a new impulse to Homeric criticism, and led to the famous Recension of the Iliad by the German scholar, Frederick Augustus Wolf, in 1795.Previous to Wolf, the idea that Homer was not the sole author of epics ascribed to him had been suggested by Bentley, Rousseau, and others in modern times, and, it is said, by Josephus, Cicero, and others in ancient times. But no serious attempt at proof had ever been made until Wolf, in his revolutionary Prolegomena (preface to his edition of the Iliad), shook the literary world to its foundations, and inaugurated a new era of literary criticism.
The celebrated Wolfian theory, is in the main, as follows:(1) Alphabetic writing, according to Wolf, was not known to the Greeks until about 600 B. C. There is no evidence that the laws were written until that time, and certainly a prose literature, which calls for writing, was not in existence previously. It is true that many verses were older, but verse was the original form of extemporaneous oratory or chanting, and the profession of rhapsodist was that of one who recites from memory.(2) In Homer himself, there is but a single mention of a message by characters, [i.e., letters] and that is the case of Bellerophon, "who bore tokens of woe, graven on a folded tablet, many deadly things," to the King of Lydia. This was in some form a written message to the king, in which the writer requests him to slay Bellerophon, and it was not until the tenth day of Bellerophon's visit that the king asked to see "what token he bore." Now, this token on the folded tablet does not by any means imply alphabetic writing, and throughout the rest of the poems we hear of no communication as passing between any of the chiefs in Troy and their families at home.(3) Even if letters were known, nobody read, and wooden or leaden tablets were unable to contain lengthy works. If the poems were not written, it is impossible that the text could have been preserved from corruption during several centuries.(4) Besides, there are manifest discrepancies in the poems themselves. In one case a chief, who has been killed in an early book, is made to attend the funeral of his son in a later book, and there are other discrepancies of time, place and style.(5) Then, too, the exploits of all the chiefs have nothing to do with the story of the Wrath of Achilles, and are manifestly inserted to glorify local heroes. These are the main grounds of the Wolfian theory.The conclusion is that the Iliad is a series of short songs put together in a later age. In regard to the Odyssey, the opinion of the Wolfian school is that it is of different authorship altogether from the Iliad.
Wolf's theory has been violently attacked, learnedly defended, and largely elaborated. Grote, the historian of Greece, makes two distinct works of the Iliad: One he calls the Wrath of Achilles, mainly by Homer; the other the Iliad composed of floating songs. Lachmann, a celebrated German scholar, finds in the Iliad all the joints of sixteen small works.Mr. Walter Leaf has recently issued his edition of the Iliad, compiled by getting together twenty-six passages from different books of the poems. He, of course, has scholarly reasons for considering all the rest spurious. "The Nation," in reviewing this work, declares that"in a century after the promulgation of the Wolfian idea (that is, in 1895), the number who believe in the theory of genuineness of Homer's works as traditionally received, will be so small that first-class scholars will not consider it worth while to waste time in endeavoring to convince them of its untenableness."A singular feature in all these later criticisms is the fact that the very noblest portions of the poem are considered not Homeric. The embassy to Achilles, containing the finest eloquence of the poem; the meeting of Achilles and Priam, containing the noblest pathos–these and other passages of like significance are relegated to floating songs of unknown poets, and the Iliad becomes to the layman a Hamlet without the Prince.
But the Wolfian theory and its progeny have not gone unchallenged by eminent scholars. The English critics are its choicest defenders. The answers to the theory are mainly these:First. Writing may have existed at the time of Homer, for the Greeks were in close communication with the Phoenicians as early as 1100 B. C. The Phoenicians were skilled in writing, and the quick-witted Greeks would not be slow to imitate so useful an art.Second. Even if writing were unknown, transmission by memory was not at all impossible. Rhapsodists were a professional class, trained purely for the purpose of memorizing, and the public recitations in which each might criticise the other, insured the integrity of the text. Extraordinary feats of memory are not unknown in our own times. Macaulay could, without effort, recite half of "Paradise Lost;" Dr. Bathurst is said to have known the whole Iliad in Greek when a boy. If such performances are possible by non-professional reciters in an era when writing has weakened the power of memory, they certainly were not impossible in a trained and picked class of memorizers who could not depend on writing.Third. There are discrepancies, it is true; but they are only such as might occur in long poems by a single author, especially if not written; and while some interpolations may be granted, they are not sufficient to disturb the general integrity of the text.Fourth. The plots are essentially bound together by an underlying unity; the style and turn of language and thought in both poems are those of the one master; and if the author of the Iliad and he of the Odyssey are not the same, then nature must have produced bountifully the supreme poetic inspiration when the world was young.This is, in very small mold, the modern Homeric question; its bibliography is enormous, although the controversy is really in its incipiency. ..."- N.M. Cohen, Homer And His Poems, (Chicago, 1893) p 120-121