§ IFormulation
Everything that happens is a link in the single chain of causes (TERMεἱμαρμένη), identical with the reason of the cosmos. Vexation at what happens is therefore vexation at the rational order itself, of which the human being is a part. The sage accepts every event as occurring κατὰ φύσιν — not because it is "pleasant," but because non-acceptance is a category error: it demands that the whole be ordered otherwise, and this is meaningless. This act of assent to what happens is what Hadot calls "the discipline of desire" (φιλεῖν τὸ συμβαῖνον — "to love what happens").
§ IISources in tradition
SVF II 974–975 (Chrysippus on fate and assent); the classical formulation in Cleanthes' hymn to Zeus — ἄγου δέ μ', ὦ Ζεῦ, καὶ σύ γ' ἡ Πεπρωμένη ("lead me, Zeus, and you, Destiny," SVF I 527, cited in Epict. Ench. 53); Cic. De fin. III 75; Sen. Ep. 107.11; Epict. Ench. 8 ("do not wish that what happens should happen as you would have it; wish that it should happen as it does"). In Marcus: Med. 2.2; 4.34; 05-08; 05-10; 05-23 (consider the speed of the flux of things — accept the flow); 05-24 (you are a tiny part of substance and time: accept your lot); 05-27; 06-39 (adapt to your lot, συνάρμοζε; and love the co-allotted truly); 06-44 (what the gods send by the common sequence — to welcome and love); 06-49 (contentment with the allotted span — as with the allotted substance, στέργεις); 07-41 (a verse of Euripides: even neglect by the gods "has its λόγος"); 07-46 (Plato, Gorgias: entrust the span to god — none escapes fate; consider only how to live it best); 07-51 (a verse: bear the wind from god without lament, ἀνοδύρτοις); 07-54 (θεοσεβῶς εὐαρεστεῖν τῇ παρούσῃ συμβάσει — the first member of the triad); 07-57 (the purest formula: love only τὸ συμβαῖνον καὶ συγκλωθόμενον — what is "spun together with you"); 07-68 (πᾶν τὸ συμβαῖνον ἐξοικειοῦται — all is "made kin," neither new nor unmanageable); 08-05 (μὴ ταράσσου: all is by the nature of the Whole; not to be troubled at the world's order); 08-06 (πάντα τροπαί, μή τι καινόν — not to fear change as though "new"); 08-07 (ἀσπάζεσθαι τὸ ὑπὸ τῆς κοινῆς φύσεως ἀπονεμόμενον — to welcome what the common nature assigns); 08-09 (not to grumble at court life or one's own); 08-15 (not to wonder at what the world produces by nature — as the fig-tree its figs); 08-18 (the elements change "and do not murmur" — οὐ γογγύζει); 08-20 (the end is an equal phase, no evil: the ball's descent is planned); 08-32 (to be content with the hindrance and shift good-temperedly to what is allowed); 08-34 (whoever will not accept what happens cuts himself from the Whole); 08-35 (to accept the hindrance = to turn it into one's own material); 08-43 (not to turn from what befalls people, but to receive it with kindly eyes); 08-45 ("cast me where you will" — the daimon is propitious everywhere); 08-46 (each meets only what is natural to it; the common nature brings nothing unbearable); 08-50 (do not add "why is there such a thing?" — throw the bitter cucumber, turn from the brambles); 09-03 (εὐαρέστει τῷ θανάτῳ — be glad of death as one of the things nature wills); 09-06 (εὐαρεστική διάθεσις — glad acceptance of all from the "external cause": the third member of the triad of disciplines); 09-35 (loss = change, in which the nature of the Whole "delights" (χαίρει) — to accept the loss as a change of form); 09-37 (ἅλις τοῦ γογγυσμοῦ — "enough of murmuring": murmuring is precisely the refusal to accept what is given); 10.5; 10-06 (εὐαρεστήσω παντὶ τῷ ἀποβαίνοντι — "I shall be well pleased with all that comes about," as the citizen welcomes what the city assigns); 10-08 (σύμφρων = ἑκούσιος ἀπόδεξις — the "willing acceptance" of what the common nature allots); 10-11 (φιλεῖ τὸ νῦν ἀπονεμόμενον ἑαυτῷ — he loves the present allotment, does not merely put up with it); 10-14 (δὸς ὃ θέλεις· ἀπόλαβε ὃ θέλεις — the decision handed over entirely to nature); 10-20 (καὶ τότε συμφέρει ὅτε ἐκείνη φέρει — the benefit coincides with the event in time; it is not to be discovered later); 10-21 (σοὶ συνερῶ — "I shall co-love with you": the nearest Marcus comes to the formula amor fati itself); 10-22 (the trilemma exhausted — οὐκοῦν εὐθύμει, a conclusion rather than a consolation); 10-25 (not to want what has been, is, or will be — desertion in all three tenses); 10-28 (ἑκουσίως ἕπεσθαι — to follow willingly is given to the rational alone; to follow bare is necessary for all); 10-35 (a healthy mind "must stand ready for everything that happens," as a healthy eye for everything visible: acceptance derived from physiology, not from will); 10-36 (οὐ μὴν ἀνθελκόμενος ἀλλ’ ἀβιάστως — "not dragged back, but without violence": acceptance taken at its narrowest point, in parting from people who want you gone); 11-06 (ἔχει λόγον καὶ τοῦτο — "there is reason in this too," a line of Euripides taken as a formula of acceptance); 11-07 (no setting of a life is fitter for philosophy than your present one: the wish for another is removed by devaluing its object); 12.14. The Latin phrase amor fati as a term is late (Nietzsche, Ecce Homo), but it captures the Stoic content precisely. In Book XII — 12-01 (ὁσιότης is defined through φιλεῖν τὸ ἀπονεμόμενον, "to love what is allotted": piety just is consent to one's lot); 12-03 (θέλουσαν τὰ συμβαίνοντα, "willing what happens" — the second member of the triad of disciplines). Cf. also 12-11 (δέχεσθαι πᾶν ὃ ἂν νέμῃ αὐτῷ ὁ θεός — to accept everything God apportions); 12-13 (the man astonished at anything whatever is declared ridiculous and a stranger); 12-23 (καλὸν ἀεὶ πᾶν καὶ ὡραῖον τὸ συμφέρον τῷ ὅλῳ). In Books I–IV the dogma appears now negatively, as a ban on grumbling: 02-05 (δυσαρέστησις πρὸς τὰ συμμεμοιραμένα), 02-13, 02-16 (τὸ δυσχεραίνειν τινὶ τῶν γινομένων), 04-29; now positively, as acceptance: 02-17 (τὰ συμβαίνοντα καὶ ἀπονεμόμενα δεχόμενον), 03-04 and 03-16 (ἀσπάζεσθαι τὰ συμβαίνοντα), 04-03 and 04-25 (τοῖς ἐκ τῶν ὅλων ἀπονεμομένοις), 04-33 (διάθεσις ἀσπαζομένη πᾶν τὸ συμβαῖνον ὡς ἀναγκαῖον). Separately — 04-01 (the readiness to shift easily to what is possible and given), 04-23 (nothing early or late that is timely for the Whole), 04-26, 04-31 (entrusting all one's own to the gods), 04-34 (giving oneself over to Clotho), 04-48 (ἵλεων καταλῦσαι).
§ IIINotes
In 02-02 this doctrine stands in the closing imperative: "do not be vexed at your present lot, and do not fear what is to come." Linked to dichotomy-of-control: what is not up to us is also not a topic for discussion — it has already happened or will happen by nature. The objection usually directed at this doctrine ("it means putting up with injustice") does not work in Stoic coordinates: consent to what happens does not annul action; it only relieves the ruling part of the unnecessary burden of protest — so that action can be precise rather than reactive. From the Epictetan run at the end of Book XI: 11-33 (to look for the child who "is no longer given" is the same madness as looking for a fig in winter) and 11-34 (αὔριον ἴσως ἀποθανῇ — the acceptance is directed not at the event but at its possibility, and is said inwardly, in the act of kissing).