All that has hitherto been stated has regard to the general principles only of the Stoics touching the end and the conditions of moral action. Whether the mere exposition of principles be enough, or whether the practical application of these principles to the special relations of life does not also form part of moral science—is a question as to which the Stoic School was not originally unanimous. Aristo, a Cynic on this as on other points, was of opinion that this whole branch of moral science is useless and unnecessary; the philosopher must confine himself exclusively to things which have a practical value, the fundamental ground of morality. [748] Within the Stoic School, however, this view did not gain much support. Even Cleanthes, who otherwise agreed with Aristo, did not deny the value of the application of theory to details, provided the connection of details with general principles were not lost sight of. [749] Nor can there be any doubt that, after the time of Chrysippus, details engrossed much of the attention of the Stoic philosophers. Posidonius enumerates, as belonging to the province of moral philosophy, precept, exhortation, and advice. [750] His teacher, Panætius, had discussed the hortatory side of morality [751] in three books on duties, which are imitated in Cicero’s well-known treatise. [752] The division of ethics attributed to Diogenes, [753] and by him referred to Chrysippus, leaves place for such discussions; [754] and, not to mention Aristo’s opposition, which supposes the existence of applied moral science, the example of his fellow-student Persæus, whose precepts for a science of banqueting [755] have been already referred to, proves how early practical ethics had obtained a footing within the Stoic School. Moreover, the elaborate theory of virtue propounded by Chrysippus and his followers [756] can hardly have failed to include many of the principal occurrences in life. Thus a number of particular precepts are known to us, which are partly quoted by other writers as belonging to the Stoics, and are partly to be found in the pages of Seneca, Epictetus, and Marcus Aurelius, and in Cicero’s treatise on duties. Indeed, the Stoics were the first who went at all deeply into the subject of casuistry. [757] At a later epoch, when more general questions had been settled by Chrysippus, the preference for particular enquiries within the domain of applied moral science appears to have increased among the Stoics. [758] Probably none but the later members of the School advanced the unscientific assertion [759] that we ought to confine ourselves to precepts for particular cases, since only these have any practical value.