"Nature" is one of the central concepts of the Stoic system, used in several senses: (1) the nature of the whole, identical with god-as-Logos and the cosmic order; (2) the nature of the human being — rationality and sociality; (3) the nature of a particular thing — its essential constitution. The Stoic imperative — "to live in agreement with nature" (ὁμολογουμένως τῇ φύσει ζῆν) — means simultaneously to follow the cosmic law and to realise one's own rational-social essence.

SVF I 179 (Zeno, the formula "to live according to nature"); III 4–9 (Chrysippus' development of the formula); DL VII 87–89; LS 63. In Marcus: Med. 2.1; 2.9; 2.16; 4.51; 05-01 (at dawn: "I rise to do a human's work," κατὰ φύσιν); 05-03; 05-04 (I walk the road of nature until I fall and rest); 05-08 (nature "prescribed" what befalls you, as Asclepius prescribes a cure); 05-09 (not to flag if you do not act from right dogmas at every point); 05-10 (to contemplate the hidden nature of things); 05-15 (only what accords with a human's nature is proper to a human); 05-25 (κοινὴ and ἐμὴ φύσις — what the common nature wills me to have, what my own wills me to do); 05-29 (to live by the nature of a rational and social being); 06-09 (κατὰ τὴν τῶν ὅλων φύσιν — all is accomplished by the nature of the Whole, not by any other); 06-33 (toil in one's own function is not παρὰ φύσιν, hence no evil); 06-40 (in things held together by nature the making power abides within); 06-44 (my nature is rational and social); 06-58 (to live by the reason of one's own nature; nothing against the common nature); 07-05 (the mind — an instrument given by the nature of the Whole); 07-11 (for the rational being κατὰ φύσιν and κατὰ λόγον are the same); 07-18 (what is dearer or more proper to the nature of the Whole than μεταβολή); 07-23 (nature moulding the universal substance as wax); 07-24 (the scowling face — λίαν παρὰ φύσιν); 07-25 (the governing nature will change all, that the world may be ever young); 07-28 (the nature of the rational ruling part — to be sufficient to itself in just action); 07-55 (the double φύσις leads: the Whole's through what happens, one's own through what must be done); 07-56 (live the remainder κατὰ τὴν φύσιν, as a surplus); 07-67 (φύσις has not so blended you with the body that you cannot circumscribe yourself); 07-74 (benefit is an act κατὰ φύσιν; in benefiting you receive); 07-75 (the φύσις of the Whole set out on world-making — the disjunction about the now); 08-01 (the good — to do what man's nature requires); 08-05 (remember what man's φύσις demands, and that all is by the nature of the Whole); 08-06 (ἡ τῶν ὅλων φύσις — the nature of the Whole transposes and transforms all); 08-07 (πᾶσα / λογικὴ φύσις "fares well"; the leaf as part of the plant's nature); 08-12 (κατὰ τὴν ἀνθρωπικὴν φύσιν — to rise for social work, not to sleep like the animals); 08-20 (φύσις aims at the end no less than the beginning — ball, bubble); 08-29 (ἐξουσία κατὰ φύσιν — the power to keep the soul clean, one's own by nature); 08-35 (ἡ τῶν λογικῶν φύσις gave the power to turn a hindrance into material); 08-41 (a hindrance to mind is an evil to νοερὰ φύσις; the ladder of natures); 08-46 (ἡ κοινὴ φύσις brings nothing unbearable; to each what is natural to it); 08-50 (ἡ τῶν ὅλων φύσις has nothing outside — the enclosed, self-sufficient artist); 09-01 (injustice and lying are impiety against φύσις, which is truth; evenness toward the indifferent as piety); 09-03 (death is one of "nature's operations," φυσικὰ ἐνεργήματα); 09-09 (κρατεῖ ἡ φύσις — "nature prevails": it draws the rational to union as water to flow down); 09-29 (ποίησον ὃ νῦν ἡ φύσις ἀπαιτεῖ; did they know what ἡ κοινὴ φύσις willed?); 09-31 (the social act is κατὰ φύσιν for a rational-social being); 09-35 (ἡ τῶν ὅλων φύσις "delights" in change — all comes to be well κατὰ φύσιν); 09-42 (ἡ φύσις has given man the antidote-virtue; an act κατὰ φύσιν τὴν σήν is itself the whole reward); 10-02 (the ladder of the three φύσεις — vegetative, animal, rational-social); 10-03 (πέφυκας φέρειν — what you are by nature able to bear); 10-06 (the premise: I am a part of the Whole governed by nature; the nature of the cosmos has no outside); 10-07 (φύσει περιέχεται — nature could neither design evil for her parts nor let it happen unawares); 10-08 (the κοινὴ φύσις allots, and the σύμφρων accepts what is allotted); 10-11 (in all that is not his own a man gives himself up τῇ τῶν ὅλων φύσει); 10-14 (ἡ πάντα διδοῦσα καὶ ἀπολαμβάνουσα — "give what you will; take back what you will"); 10-15 (let them examine a man κατὰ φύσιν ζῶντα); 10-18 (καθότι ἕκαστον πέφυκεν ὥσπερ θνῄσκειν — the mode of dissolution is set by each thing's nature); 10-20 (ἡ τῶν ὅλων φύσις brings — and what is brought is thereby beneficial); 10-33 (ἀπόλαυσιν δεῖ ὑπολαμβάνειν πᾶν ὃ ἔξεστι κατὰ τὴν ἰδίαν φύσιν ἐνεργεῖν — one must reckon as enjoyment everything one is free to do according to the nature proper to oneself); 10-36 (ἡ φύσις συνῆψέ σε καὶ συνέκρινεν, ἀλλὰ νῦν διαλύει — two verbs of binding against one of release; and the parting is named "one of the things according to nature"); 11-05 (θεωρήματα περὶ τῆς τοῦ ὅλου φύσεως — knowledge of the nature of the Whole as one of the two branches without which "being good" does not come about); 11-10 (οὐκ ἔστι χείρων οὐδεμία φύσις τέχνης — the argument from imitation: the arts imitate natures, hence the most complete nature does not fall short of the ingenuity of craft, and justice is derived from this); 11-13 (both natures in one sentence: to do τὸ τῇ φύσει σου οἰκεῖον and to accept τὸ τῇ τῶν ὅλων φύσει εὔκαιρον); 11-20 (five vices — injustice, licence, anger, grief, fear — are defined by a single phrase: ἀφισταμένου τῆς φύσεως, "a standing away from nature"); 11-34 (φυσικοῦ τινος ἔργου σημαντικόν — a word that signifies a work of nature cannot be an ill omen). In Book XII — 12-01 (φύσις "brought your lot to you and you to it"; and fear is redefined as the fear of never having begun to live κατὰ φύσιν); 12-05 (had another order been κατὰ φύσιν, "nature would have brought it about" — nature as the criterion of the possible). And 12-11 (τὸ ἑξῆς τῇ φύσει); 12-23 (φύσις appoints the καιρός and the ὅρος — sometimes one's own, in old age, but in every case the nature of the whole). And 12-26 (πάντα κατὰ τὴν τῶν ὅλων φύσιν γίνεται — the first item in the list of what is forgotten); 12-32 (ποιεῖν by one's own φύσις, πάσχειν by the common one); 12-36 (what sends you out of the city is no tyrant and no judge but ἡ φύσις ἡ εἰσαγαγοῦσα — she who brought you in). In Books I–IV φύσις runs throughout: 02-03, 02-09, 02-12, 02-17; 03-02 (τοῖς φύσει γινομένοις — "what comes about by nature"), 03-04 (a man's nature as the measure of care for others), 03-09, 03-11, 03-12 (κατὰ φύσιν); 04-01, 04-05, 04-09, 04-23, 04-24, 04-29, 04-36 (the φύσις of the Whole), 04-39, 04-48 and 04-51 (κατὰ φύσιν), 04-49 (τῆς φύσεως τοῦ ἀνθρώπου).

In 02-01 φύσις occurs three times: (1) "the nature of the good," (2) "the nature of evil," (3) "the nature of the one who errs." This triple invocation sets the structure of the whole passage: knowledge of three natures — the good, the bad, the human — frees us from the passions. The end of the passage returns to φύσις in negative form: "to act against one another is contrary to nature" (παρὰ φύσιν). The ethical norm is thereby derived from ontology: what breaks TERMcooperation also breaks the bond with the cosmos.