Seneca on gratitude and justice: how to translate Ep. 81, 19?

In this paper I discuss how to translate a rather ambiguous passage in Seneca’s “Letters to Lucilius” (81, 19), where he either I) opposes gratitude to justice for the reason that the former is the agent’s own good and the latter regards other people’s interests or, II) quite to the contrary, draws an analogy between these virtues, pointing out that both of them constitute the agent’s own good. Both these alternatives seem grammaticaly possible and can be found in modern translations of this “Letter” into main European languages. I argue in favour of II) on the ground that it agrees better with general perfectionist approach to virtues that Seneca espouses in this context.