Of these the oldest, Kb, is the best; and though not without many ordinary errors, it is comparatively free from emendation. The next oldest, Lb, is not quite so good, but its variants must be weighed on their merits. The four more recent mss. are of little value. Ha and are usually ignored by Bekker, as their unique readings are idle variants or corruptions. MP and Ob are rather better, but their variants when not worthless are mostly due to emendation. In the present edition these four mss. are only quoted when preferred to both Kb and Lb.
Other mss. have been collated by other scholars, but none has any authority; now and then their readings are preferable on their merits, and a few of these have been quoted here from Susemihl.
Another witness, ranking in importance next to the two best mss.; is the thirteenth-century Latin translation(Γ) attributed to William of Moerbeke, which is the basis of the commentary of St. Thomas Aquinas. This version follows the Greek as closely as Latin idiom permits, and is almost equivalent to another Greek mss.; it occasionally shows an independent tradition of the text.
Some textual value attaches to the commentary of Aspasius (Asp.), second century a.d. (edited by Heylbut 1889), but only where we can be sure that he is quoting and not merely paraphrasing Aristotle, and that his quotations have not been assimilated by copyists to their mss. of Aristotle. His text differed little from our mss., and constantly confirms the antiquity of their questionable readings; it generally supports Kb, sometimes Lb, and rarely gives a new variant. A similar use can be made
of the commentary of Alexander of Aphrodisias, c. 200 a.d.
A few variants of interest have been gleaned by the industry of scholars from the Greek paraphrase of Heliodorus (Hel.), 1367, the Latin translations of Aretinus (Ar.), 1473, Argyropylus, 1473, and Felicianus, 1542, and the Aldine editio princeps (Aid.) of the whole of Aristotle, 1495–1498.a
The above Introduction was written for the first edition of this Book in 1926.
In preparing a new edition I have made a few additions to it and a good many alterations in the text, translation and notes. Some I have discussed in the journals to which references are given in the footnote on p. xxiv above. I have had the advantage of consulting Mr Ross’s brief notes in his translation (re-issued 1931).