  In the passage quoted, Marcus explains how one might do what is in one’s nature by saying that one must modify one’s beliefs about good and bad, as these inform one’s impulses and actions.  He says, for example, that if we believe that pleasure is good and pain evil, then we will be resentful of the pleasures enjoyed by the vicious and the pains suffered by the virtuous. And if we are resentful of what happens, we will be finding fault with Nature and will be impious (ix.3). But while false beliefs about good and bad hinder us from following nature and acting virtuously, how can their removal by itself enable us to follow nature and act virtuously? Once I know that pleasure and pain are neither good nor evil but are indifferent for my happiness, I still need to know how I should respond to this pleasure and that pain, in order to be following nature. The first century Stoic philosopher Seneca argues in his Letters to Lucilius for the usefulness of concrete advice for certain types of situations (praecepta) on the grounds that having eliminated vice and false opinion, one will not yet know what to do and how to do it (94.23), for inexperience, not only passion, prevents us from knowing what to do in each situation (94.32); Seneca also says that nature does not teach us what the appropriate action is in every case (94.19). Perhaps Marcus thinks that there is, in every choice situation, something one can do that is productive of virtue (he says, ‘nothing is good for a human being which does not make him just, temperate, courageous, free’; on the other hand, ‘make’ may have the sense of constituting rather than producing, in which case the reference to the virtues in the passage isn’t action-guiding at all). Alternatively, he may think that what produces virtue is not the content of one’s action, but the thoughts that go along with it. But what thoughts are these? Surely, if virtue is to have any content, thinking ‘only virtue is good’ is not going to be sufficient.