have received a more favourable treatment at the hands of Aristo, had he not shared the opinion of Socrates, that it is a branch of knowledge which transcends the capacity of the human mind; [85] and having once embraced this notion, he was inclined to pronounce all physical enquiries useless. His attitude towards other sciences has therefore been generally expressed by saying that he excluded from philosophy both logic and natural science, on the ground that both are useless; the former being irrelevant, and the latter transcending our powers. [86] Even ethics was limited by Aristo to most fundamental notions—to enquiries into good and evil, virtue and vice, wisdom and folly. The special application of these notions to the moral problems suggested by particular relations in life, he declared to be useless and futile; proper for nursemaids and trainers of young children, but not becoming for philosophers; [87] wherever there is a proper knowledge and a right disposition, such particular applications will come of themselves without teaching; but when these are wanting, all exhortations are useless. [88] [(b) Views of Zeno and Cleanthes.] These views are mentioned as peculiar to Aristo, and as points in which he differed from the rest of his School; and, to judge from his controversial tone, the opposite views were those almost universally entertained by Stoics. That controversial tone, in fact, appears to have been directed not only against assailants from without—such as the Peripatetics and Platonists—but far more against those members of the Stoic School, who attached greater importance than he did to special ethical investigations, and to logical and physical enquiries. Among their number must have been Zeno and Cleanthes; for Zeno set the example to his School of dividing philosophy into logic, ethics, and natural science; [89] witness the titles of his logical and physical treatises [90] and also the statements in reference to theoretical knowledge and natural science which are expressly attributed to him. Moreover, Zeno himself recommended to others, and himself pursued, logical enquiries. [91] Indeed, his whole mental habit, [92] with its keen appreciation of even the subtleties of the Megarians, bears testimony to an intellectual type of thought which is far removed from that of Aristo. [93] It was, moreover, Zeno who chose that curt and unadorned logical style, which is found in its greatest perfection in Chrysippus. [94] Logical and scientific treatises are also known to have been written by Cleanthes, [95] who, in his division of philosophy, allotted separate parts to logic, to rhetoric, and to natural science, [96] and the name of Cleanthes is one of frequent occurrence, not only in the natural science, but more particularly in the theology of the Stoics. Still more exhaustive enquiries into logic and natural science appear to have been set on foot by Sphærus. [97] These prove that the energies of the Stoic School must have been