The different works now remaining, and published in the Berlin edition of Aristotle, are forty-six in number. But, among these, several were disallowed or suspected even by some ancient critics, while modern critics have extended the like judgment yet farther. Of several others again, the component sections (either the _books_, in our present phraseology, or portions thereof) appear to have existed once as detached rolls, to have become disjointed or even to have parted company, and to have been re-arranged or put together into aggregates, according to the judgment of critics and librarians. Examples of such doubtful aggregates, or doubtful arrangements, will appear when we review the separate Aristotelian compositions (the Metaphysica, Politica, &c.). It is, however, by one or more of these forty-six titles that Aristotle is known to modern students, and was known to mediæval students. But the case was very different with ancient _literati_, such as Eratosthenes, Polybius, Cicero, Strabo, Plutarch, &c., down to the time of Alexander of Aphrodisias, Athenæus, Diogenes Laertius, &c., towards the close of the second century after the Christian era. It is certain that these ancients perused many works of Aristotle, or generally recognized as his, which we do not now possess; and among those which we do now possess, there are many which it is not certain that they perused, or even knew. Diogenes Laertius, after affirming generally that Aristotle had composed a prodigious number of books ([Greek: pa/mpleista bi/blia]), proceeds to say, that, in consequence of the excellence of the author in every variety of composition, he thinks it proper to indicate them briefly.[1] He then enumerates one hundred and forty-six distinct titles of works, with the number of books or sections contained in each work. The subjects are exceedingly heterogeneous, and the form of composition likewise very different; those which come first in the list being Dialogues,[2] while those which come last are Epistles, Hexameters, and Elegies. At the close of the list we read: "All of them together are 445,270 lines, and this is the number of books (works) composed by Aristotle."[3] A little farther on, Diogenes adds, as an evidence of the extraordinary diligence and inventive force of Aristotle, that the books (works) enumerated in the preceding list were nearly four hundred in number, and that these were not contested by any one; but that there were many other writings, and _dicta_ besides, ascribed to Aristotle--ascribed (we must understand him to mean) erroneously, or at least so as to leave much doubt.[4] [Footnote 1: Diog. La. v. 21. [Greek: Sune/grapse de\ pa/mpleista bi/blia, a(/per a)ko/louthon ê(gêsa/mên u(pogra/psai, dia\ tê\n peri\ pa/ntas lo/gous ta)ndro\s a)retê/n.]]