From the pen of Isokrates also, we find various passages apparently directed against the viri Socratici including Plato (though without his name): depreciating,[91] as idle and worthless, new political theories, analytical discussions on the principles of ethics, and dialectic subtleties; maintaining that the word philosophy was erroneously interpreted and defined by many contemporaries, in a sense too much withdrawn from practical results: and affirming that his own teaching was calculated to impart genuine philosophy. During the last half of Plato's life, his school and that of Isokrates were the most celebrated among all that existed at Athens. There was competition between them, gradually kindling into rivalry. Such rivalry became vehement during the last ten years of Plato's life, when his scholar Aristotle, then an aspiring young man of twenty-five, proclaimed a very contemptuous opinion of Isokrates, and commenced a new school of rhetoric in opposition to him.[92] Kephisodôrus, a pupil of Isokrates, retaliated; publishing against Aristotle, as well as against Plato, an acrimonious work which was still read some centuries afterwards. Theopompus, another eminent pupil of Isokrates, commented unfavourably upon Plato in his writings: and other writers who did the same may probably have belonged to the Isokratean school.[93] [Footnote 91: Isokrates, Orat. x. 1 (Hel. Enc.); Orat. v. (Philipp.) 12; Or. xiii. (Sophist.) 9-24; Orat. xv. (Permut.) sect. 285-290. [Greek: philosophi/an me\n ou)=n ou)k oi)=mai dei=n prosagoreu/ein tê\n mêde\n e)n tô=| paro/nti mê/te pro\s to\ le/gein mê/te pro\s to\ pra/ttein ô(/phelou=san--tê\n kaloume/nên u(po/ tinôn philosophi/an ou)k ei)=nai phêmi/], &c.] [Footnote 92: Cicero, De Oratore, iii. 35, 141; Orator. 19, 62; Numenius, ap. Euseb. Præp. Evang. xiv. 6, 9. See Stahr, Aristotelia, i. p. 63 seq., ii. p. 44 seq.