Stoicism was one of the dominant philosophical systems of the Hellenistic period. The name derives from the porch (stoa poikilê) in the Agora at Athens decorated with mural paintings, where the first generation of Stoic philosophers congregated and lectured. The school of thought founded there long outlived the physical Athenian porch and notably enjoyed continued popularity in the Roman period and beyond. This entry introduces the main doctrines and arguments of the three parts of Stoic philosophy – physics, logic, and ethics – emphasizing their interlocking structure. We also review the history of the school, the extant sources for Stoic doctrine, and the Stoics’ subsequent philosophical influence.
These three clauses are construed by the Stoics as providing individually-necessary and jointly-sufficient conditions for an impression to be cognitive (Nawar 2014). Together, they are supposed to capture the feature(s) shared by all and only cognitive impressions, in virtue of which they serve as criteria of truth (Diogenes Laertius, 40A). However, their precise interpretation remains highly controversial. One longstanding dispute concerns the meaning of what is as it features in clause (1): is it to be understood existentially or veridically? On the existential interpretation, what is refers to a being or real object, so that clause (1) requires the cognitive impression to be caused by (arise from) an existing object in the external world. So construed, clause (1) rules out cases where an impression is formed solely through the activity of the mind (e.g. in a hallucinatory episode). However, this
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Textually, the Greek phrase translated by Long and Sedley as what is does not use a form of to be (einai) but rather a different, technical expression: to obtain (huparchein). According to Stoic metaphysics (see above, 2.1), only bodies are or exist (einai), and so if clause (1) were intended to refer specifically to external objects (bodies), we would expect a form of einai, not huparchein. Philosophically, the existential reading implies there are only cognitive impressions of bodies. However, the Stoics acknowledge the possibility of cognition concerning incorporeal propositions, for instance, truths about the nature of the gods (Diogenes Laertius, 40P), and insofar as cognition consists in an assent to a cognitive impression, there should be cognitive impressions of these true incorporeal propositions as well. (On this issue, see Schwab forthcoming, and the recent exchange between Vogt 2022 and Nawar 2022.) The
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On this reading, what is picks out a true proposition, in line with the Stoic claim that true propositions obtain rather than exist (cf. Sextus, 34D) and with further evidence in Cicero (cf. 40I and Acad. 2.112). Thus clause (1) amounts to a veridicality requirement: all cognitive impressions must be true. Moreover, a veridical reading of clause (1) would also seem to allow for the possibility that there are cognitive impressions of true propositions, though this point is controversial: see Sedley 2002 and Nawar 2014. For an effort to rehabilitate a version of the existential reading, see Stojanovi 2019 and Caston forthcoming.
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The major debate over clause (2) turns on whether it serves to characterize the cognitive impressions phenomenological character, causal history, or both, and ones stance on this question affects ones interpretation of clause (3) in turn. Both Cicero and Sextus report that clause (3) was added by Zeno to an earlier definition
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