Apatheia is one of the most consistently misread Stoic terms. In modern English, apathy connotes indifference, listlessness, not caring. Apatheia in Stoic Greek means none of these. It means freedom from the pathē — the four disordered passions (appetite, pleasure, fear, distress) — and nothing more.
The Stoic sage in apatheia is not without feeling. He has the three eupatheiai — joy, caution, and rational wish. He cares about virtue. He cares about the welfare of others. He flinches at sudden noises (the propatheia). What he does not have are the disordered passions that arise from mistaken assent to impressions about indifferents.
The misreading is old. Early Christian writers — Tertullian, Lactantius — attacked the doctrine of apatheia as if it were a doctrine of inhuman impassivity. (Tertullian was not a flat opponent of the Stoa; he borrowed Stoic ontology in other works, and the attack on apatheia was directed at this specific doctrine rather than the school as a whole.) The Stoics themselves spent considerable energy clarifying that the impassivity reading was a caricature. (See Cicero's Tusculan Disputations 4 for the most extended ancient exposition.)
The practical implication for the prokoptōn: the goal is not to feel nothing. The goal is to feel rightly — with feelings that match the actual value-status of the objects involved. Joy at present goods correctly identified. Caution toward future evils correctly identified. Rational wish toward future goods correctly identified. Less of the disordered passions, not less feeling.
A test for whether one is approaching apatheia or merely numb: are the eupatheiai increasing as the pathē decrease? If joy is growing as anger fades, the practice is working. If both are fading, what is left is not Stoic detachment — it is depression or affective blunting, and a different problem.