to Heraclides, and Pollis; five volumes of Dialectic Arguments, which admit of no solution, addressed to Dioscorides; an essay, in one book, against the Method of Arcesilaus, addressed to Sphærus.
The tenth set contains, a treatise in six books, against Custom, addressed to Metrodorus; and another, in seven books, on Custom, addressed to Gorgippides.
There are, therefore, works on Logic, in the four grand classes which we have here enumerated, embracing various questions, without any connection with one another, to the number of thirty nine sets, amounting in the whole to three hundred and eleven treatises on Logic.
The next division comprises those works which have for their object, the explanation of Moral Ideas.
The first class of this division, contains an essay, giving a description of Reason, addressed to Theosphorus; a book of Ethical questions; three books of Principles, to serve as the foundation of Dogmas, addressed to Philomathes; two books of definitions of Good-breeding, addressed to Metrodorus; two books of definitions of the Bad,