Hypolēpsis literally means "that which is taken under [consciousness]," from ὑπολαμβάνω ("to suppose," "to take to be"). In Stoic technical terminology, it is the evaluative judgment that the TERMruling part makes about an TERMimpression. The chain of cognitive-emotive acts runs: an impression arrives in the soul → the ruling part gives it TERMassent → a hypolēpsis is fixed in place ("I take it that this is such-and-such and worth such-and-such") → from that hypolēpsis arises an impulse (TERMὁρμή) → if the hypolēpsis contains a false evaluative content, a TERMpassion is born.

In Aristotelian usage (De anima III 3, 427b25), ὑπόληψις is a broader cognitive category: one of the ψυχικαὶ δυνάμεις, covering ἐπιστήμη (knowledge), δόξα (opinion), and φρόνησις (practical wisdom). The Stoics narrow the term in an ethical direction: for them ὑπόληψις is always already an axiologically loaded opinion, not a neutral propositional attitude. This is why work on the passions is work on one's ὑπολήψεις.

In Marcus, ὑπόληψις is one of the most frequent terms and one of his programmatic anchors. The famous formula is πάντα ὑπόληψις — "all is judgment" (Med. 2.15; 12.8; 12.22). The idea is simple and radical: things have no intrinsic affective charge; whatever stirs passion in the soul has passed through the soul's own evaluative judgment. To change the judgment is to change the world for me. This is one of the strongest therapeutic intuitions of Stoicism, and roughly every second passage of the Meditations rests on it.

Aristot. De an. III 3, 427b25 — 428b9 (the classical statement of ὑπόληψις as a generic category); SVF II 92, 105–110 (Stoic theory of impression and assent); III 169 (the role of ὑπόληψις in generating ὁρμή); DL VII 47–51; Stob. Ecl. II 88 W; Cic. Acad. I 41–42 (doxography of the Stoic doctrine of assent); LS 40, 53. In Marcus, ὑπόληψις is a leitmotif: Med. 2.12; 2.15 (πάντα ὑπόληψις); 3.9 ("guard your ὑπόληψις"); 4.3, 4.7 ("remove the ὑπόληψις and the offence is removed too"); 6.8; 6.52; 7.2; 7.16; 7.26; 8.40 ("it is not the thing that disturbs you, but your ὑπόληψις about it"); 9.13; 11.16; 12.8; 12.22; 12.26.

In 02-12 ὑπόληψις makes its first appearance in Book II, and at once in two functions:

• As an object of diagnosis: «τί εἰσιν οὗτοι, ὧν αἱ ὑπολήψεις καὶ αἱ φωναὶ τὴν εὐδοξίαν παρέχουσι» — "what are these people, whose judgments and voices supply your reputation?" Here ὑπόληψις stands at the source of a false craving for fame: my desire for renown depends on the ὑπολήψεις of others, which are themselves the opinions of people who do not know what is good. Analyse the source, and the motive is unmasked.
• As an act of correct seeing: «οὐκέτι ἄλλο τι ὑπολήψεται αὐτὸ εἶναι ἢ φύσεως ἔργον» — "he will no longer suppose [death] to be anything other than the work of nature." Here ὑπόληψις is itself the therapeutic instrument: a correct judgment, achieved by analysis, releases one from fear.

The link with Epictetus: the famous formula of Ench. 5 — «ταράσσει τοὺς ἀνθρώπους οὐ τὰ πράγματα, ἀλλὰ τὰ περὶ τῶν πραγμάτων δόγματα» ("people are disturbed not by things, but by their opinions about things") — is the same doctrine in the vocabulary of δόγμα. In Marcus, δόγμα and ὑπόληψις overlap functionally: both designate an evaluative judgment fixed in the TERMruling part. The nuance differs: δόγμα foregrounds the settledness, ὑπόληψις the act of taking into consciousness. Marcus prefers ὑπόληψις.

"πάντα ὑπόληψις" is not relativism ("everything is subjective"), but a Stoic assertion of the locus of work: I do nothing directly to the world, but I work on my own ὑπολήψεις, and through them I rebuild my relation to the world. It is a constructivist thesis not in the ontological but in the operational sense: the world is objective, but my experience of the world is constituted by my judgments about it, and only at that level can I change anything.