The chapter reviews the essentials of Seneca’s positions in moral psychology as compared to those of earlier Stoics whose works he might have studied. On the material nature of the mind (or soul); on the mechanisms of thought, belief, and action; and on the nature and management of the emotions, Seneca’s views are consonant with those of his Stoic predecessors; however, his knowledge of the system is not necessarily complete, and his emphases are sometimes different. Thus, he shows some awareness of earlier discussions of phantasia (impressions) but does not explore the topic deeply; on the other hand, he gives assent and impulse the same kind of significance in ethics as Chrysippus had. Contrary to some earlier studies, this chapter does not find Seneca to be innovative as concerns volition (voluntas) or the will. Likewise, his analysis of the emotions and of involuntary emotional response finds parallel in earlier texts. For the good emotions (eupatheiai) of the Stoic sage, he seems to know only that part of the analysis that concerns joy, to which he assigns an important role in his own ethics.

Whereas in the previous chapters the influence of law on philosophy is brought up, this chapter deals the influence of law on philosophy, with regard to method. Already within early Hellenistic philosophy a shift of focus can be discerned from a virtue-centered to an action-orientated approach: in the 3rd century BCE the early Stoics had become interested in questions about the ‘appropriate actions’ that can be derived from these virtues. In the 2nd century BCE, inspired by the Roman jurists, the Roman Stoics became interested in the concrete applications of such actions or – put differently – introduced casuistry into philosophy.