Genre and place in the book. The second passage of Book IV — an extremely compressed methodological maxim of the discipline of action: a single sentence with its verb in the third-person imperative (ἐνεργείσθω, "let it be done"). After the imagistic "physics of the ruling part" in 04-01, here is a dry rule for every act. By form it is closest to gnomes like 02-08 and to the programmatic formula of action in 02-05.

The two prohibitions. The maxim is built on a double "μηδὲν… μηδὲ…": (1) μηδὲν… εἰκῇ — nothing "at random," without purpose; (2) μηδὲ ἄλλως ἢ κατὰ θεώρημα — and not otherwise than according to a "theorem" (principle). The first is the negation of aimlessness, the second the positive norm of principled action.

εἰκῇ — at random. εἰκῇ ("haphazardly, without a plan") is the antithesis of action that has a σκοπός (a mark to aim at). The same thought is unfolded in 02-07 (nothing is more wretched than the man who has no σκοπός toward which to direct every impulse) and in 02-05, where Marcus requires action "free from all εἰκαιότης" (the same εἰκ- root). For a Stoic, aimless action is not mere inefficiency but a falling-out of the rational order. εἰκῇ here is the same defect as the drift and circling of the image of aimless motion (02-07), but taken at the level of a single act: not "a life without a course" but "a gesture without a mark."

Purpose: σκοπός and τέλος. "Not at random" means: every act is referred to a σκοπός (the mark) and ultimately to a τέλος (life according to nature, the common good). The Stoics distinguish the two: τέλος is "to obtain what accords with nature" (the attainment, partly not up to me), σκοπός is "to do all that is up to me in order to obtain it" (the taking-of-aim, wholly mine). Hence the archer image (Antipater; Cic. Fin. III 22): moral worth lies in the right aim, not in the hit. So "κατὰ θεώρημα" just is the σκοπός rightly taken: the act does not guarantee the outcome, but it guarantees being done by the right rule.

θεώρημα and τέχνη. θεώρημα — "what has been discerned," a theoretical proposition, the rule of an art; συμπληρωτικὸν τῆς τέχνης — "completing the art." Every act is to be carried out by a principle that brings the τέχνη to its fullness. The implied τέχνη is the art of living (τέχνη περὶ τὸν βίον): for the Stoics virtue itself is a τέχνη — "a system of cognitions exercised together, directed to an end useful for life" (SVF I 73); φρόνησις is "the art concerning the things of life" (SVF II 909). An act "κατὰ θεώρημα" is the act of a master who knows the right rule for the case at hand, not of an amateur acting by guesswork.

The disciplines. The principal one is action: a rule for every ἐνέργημα (act). The secondary is assent: a θεώρημα is a rightly held principle — without the correct doctrine there is no correct action. For Hadot this is the core of the discipline of action (The Inner Citadel, ch. 8, "in the service of mankind"): the act is subordinated to a σκοπός, performed "with reserve" (ὑπεξαίρεσις), and directed to the common good. "Nothing at random" is the negative phrasing of the same requirement: everything active in a person must be referred to a purpose.

Stylistics. Nine words; the impersonal imperative ἐνεργείσθω is the form of a law laid on oneself, not of advice. The double μηδέ sets the rhythm of prohibition. It is the notation of a "rule for oneself," almost a clause of a statute.

Parallels. Action with a purpose and free from εἰκαιότης — 02-05, 02-07; Med. 12.20 ("undertake nothing at random or without a purpose, nor for any reason but the common good"). The purpose of action — σκοπός and τέλος; the distinction and the archer image — Antipater (Stob. Ecl. II 76 W), Cic. Fin. III 22. The negative of aimlessness — drift and circling (02-07). The definition of τέχνη — SVF I 73; φρόνησις as the τέχνη of life — SVF II 909. Virtue as the "art of living" — Cic. Fin. 3; the discipline of action — Hadot, The Inner Citadel, ch. 8.