the causal history supplied for emotional responses addresses the question 'Why does the cylinder roll?' and answers it, in brief, by pointing out that the cylinder is round.
Graver deploys the Stoic cylinder analogy to argue that emotional responses are explained by antecedent character-traits rather than by external provocations alone, making the cylinder the master figure for the proximate/primary cause distinction in Stoic moral psychology.
, Stoicism and Emotion, 2007thesis