[14] See Professor Davidson’s _The Stoic Creed_, p. 42, where it is pointed out that each of these may be subdivided so as to bring the number up to six--Physics and Theology, Ethics and Politics, Logic and Rhetoric. See also Seneca, Epist. lxxxix., where the division is discussed. For further information on the subject, the article on the Stoics in the _Encyclopaedia Britannica_ and any of the histories of philosophy, _e.g._ Erdmann or Zeller, may be consulted. [15] Cf. Professor Burnet’s _Early Greek Philosophy_ for illustration of this in earlier times. [16] Cf. footnote 2 to p. xxxiv. [17] The method was not obsolete for many centuries, even if it is yet wholly dead. On more than one occasion the study of Natural History has been advocated on account of the abundance of figures of speech that may be drawn from it! Erasmus esteemed it because of the light it threw on the classics; his insensibility to the wonders of natural forces and processes provoked Luther’s remark that “Erasmus looks upon external objects as cows look upon a new gate.” The reader of the _Q.N._ need not, therefore, regard as matter of surprise this curious medley of science and morality, which is of the very essence of the author’s principles and purpose. Seneca performs this part of his task with evident relish. He is always ready to improve the occasion, and will even go out of his way to find it. His censure of vice, his denunciation of luxury and self-indulgence, his castigation of immorality, seem to afford him a kind of morbid satisfaction. Even a note of insincerity may sometimes be suspected. He is rather too ready to display his own acquaintance with all the refinements of the vices of “good society”: perhaps it was the fault of his age to gloat over unsavoury details that a moralist would now be more anxious to conceal than to reveal.[18] [18] “There are pictures of voluptuous ease and jaded satiety which may be the work of a keen sympathetic observation, but which may also be the expression of repentant memory” (Dill, _op. cit._ p. 298).