Marble head of Epicurus
2^nd century CE, copy of a Greek statue of the 3^rd century BC
The Metropolitan Museum of Art, New York

Epistemology plays a crucial role in Hellenistic philosophies because it lays the foundations for knowledge of nature and ethics. For this reason, Hellenistic epistemologies are the first to theorize a doctrine of the criterion (cf. Striker 1996). From a historical point of view, Epicurus – even before the Stoics – was the first philosopher to establish a canon of knowledge. As we learn from Diogenes Laertius (X 30), Canonics was preparatory to Epicurus’ philosophical system and was the focus of a work entitled Canon (Kanon).

Unfortunately, we no longer have this text, but Diogenes Laertius’ account (X 31) – perhaps dependent on the Canon itself – is a very valuable source for learning that according to Epicurus the criteria of truth are sense-perceptions (aistheseis), prolepseis (prolepseis), and affections (pathe). The Epicureans added the representative applications of the mind (phantastikai epibolai tes dianoias). These criteria are the tools of knowledge; they are based on self-evidence (enargeia: cf. Ierodiakonou 2012), and are always true. Many important studies have investigated Epicurean criteriology, and especially the first two criteria, sense-perception and prolepsis.

Studies that have focused on sense-perception have primarily explored the question of the truth of aistheseis (cf. e.g. Long 1971; Taylor 1980; Everson 1990; Verde 2018a); studies on prolepsis (cf. e.g. Manuwald 1972; Glidden 1985; Hammerstaedt 1996; Morel 2007; Tsouna 2016), on the other hand, have primarily focused on the problems of empirical concept-formation and the processing of perceptual material through the activity of reasoning (epilogismos). More sporadic are studies on affections (Diano 1974: 129-280; Annas 1992: 189-199, Konstan 2007: 21-48, Prost 2012, Verde 2018b), which have been essentially concerned with investigating the problem of the epistemological and/or ethical status and application of affections in the Epicurean system. The availability of more reliable editions of Epicurean sources (Book 10 of Diogenes Laertius’ Lives of Eminent Philosophers, Epicurus’ On Nature, Books 2, 11, 25, 28, and 34, the inscription of Diogenes of Oinoanda) and of more systematic analyses of Epicureanism have made it possible to engage in a study of epistemology that is more attentive to its Classical roots.

If we exclude D. Sedley’s (1976) seminal article on Epicurus’ professional rivals, few recent studies have succinctly addressed the problem of the likely sources of Epicurean Canonics. Aside from Shorey 1901’s dated but still useful study on Plato, Epicurus, and Lucretius, Cornea 2011-2012 and Fine 2014: Ch. 7 examined the question of whether Epicurean prolepsis finds its theoretical origin in Plato as a response to the Meno’s paradox of knowledge; Verde 2020 dealt somewhat tentatively with the relationship between Epicurus’ epistemology and Plato’s Theaetetus (on the Epicurean Antiplatonism see Bloch 1993 and Erler 2017). Schmid 1936 was the first to show that Epicurus criticized the Timaeus’ theory of elements on the basis of Epicurus’ On Nature Book 14 (ed. Leone 1984), a topic confirmed by some more recent studies (Baltussen 2003; Verde 2013: 333-346). Cornea 2014 and Hahmann 2015 briefly explored the relationship between Aristotle and Epicurus with regard to the truth and deceptiveness of sense-perception, while Avotins 1980 and Verde 2016 examined the problem of the perceptual residue in Epicurus against the background of Aristotle’s Parva naturalia.

No systematic study of the Platonic roots of Epicurean Canonics has been undertaken so far. It is likely that Epicurus knew Plato’s Theaetetus, in which the relationship between sense-perception and knowledge is investigated (and rejected). A similar argument must be made for Aristotle: the theoretical and terminological influence of the De anima and of some of the Parva naturalia on Epicureanism has yet to be investigated. In addition, the more or less recent critical literature has neglected the comparison between Democritus’ and Epicurus’ epistemology and the polemical relationship between Epicureanism and other philosophical currents like Timon’s “Pyrrhonism” and the Democritean tradition (Nausiphanes).

Finally, we must also take into account that scholars are often reluctant to acknowledge that Epicurean philosophy has its own philosophical identity within the Classical tradition. For this reason, it is very important for the progress of scholarship on Hellenistic philosophy – and on the history of ancient philosophy more generally – to consistently emphasize the dialectical and critical continuity between Epicureanism and the Classical tradition through the systematic and careful study of the relationship between Epicurean epistemology and the broad (and theoretically challenging) philosophical tradition immediately preceding it.

Raphael, School of Athens, detail
In the centre: Plato and Aristotle, with their pupils
Musei Vaticani, Room of the Segnatura, Rome

Through a careful historical-philosophical examination of all the texts that are the focus of the present research, both in terms of philological and lexicographical accuracy and in terms of the completeness of the hermeneutic debate concerning them, the Project will adopt a clear methodological approach: it will focus on the remote origins of many of the epistemological issues of Epicurus’ Canonics (mainly but non exclusively) found in Plato and Aristotle, with any eye to continuity as much as radical and polemical discontinuity. To do so, we will not only make use of the works of Epicurus transmitted by Diogenes Laertius (in addition to Book 10 of Diogenes’ Lives of Eminent Philosophers more generally), but also examine other equally central sources, such as Epicurus’ On Nature, Lucretius’ De rerum natura, and Diogenes of Oinoanda’s inscription, without neglecting of course later hostile sources. In light of this methodological premise, the main philosophers who may have attracted Epicurus’ interest are Plato and Aristotle.

Polykleitos, Doryphoros
Roman marble copy after a Greek bronze original (5^th century BC)
National Archaeological Museum of Naples

Epicurean Canonics was the first epistemological doctrine to systematically address the problem of the criterion or canon of truth (see Striker 1996; see also the recent Striker 2020). But there were certainly precedents for Epicurus’ use of the terms kanon (canon) and kriterion (criterion). According to Aristotle’s Nicomachean Ethics (III 4, 1113a33), the excellent man (spoudaios) stands as a standard and measure (kanon kai metron); Plato significantly uses the term kriterion in the Theaetetus (178b6), while in (the possibly spurious) book K of Aristotle’s Metaphysics (Κ 6, 1063a2-3) we read the words to aistheterion kai kriterion. Another important source is the work Canon attributed to Polycletus (cf. Papini 2018), in which – to quote a fitting expression from Pliny the Elder’s Naturalis historia (XXXIV 55 = 40A2 DK) – the liniamenta artis were examined as if they were laws. Polycletus’ studied the criteria for symmetry and exact proportion, which in his view were best embodied by the statue of the Doriphorus (cf. Galen. PHP V, p. 425 14, p. 308 11 De Lacy = 40A3 DK). This work, therefore, confirms that kanon was a term originally used (in a non-metaphorical sense) in the artistic field, or in the generic field of techne; kanon indicated the rule or square, i.e. a measuring instrument used by masons and carpenters (cf. Plat. Phlb. 56b). Only later, with Epicurus for the first time and then with the Stoics, did the term take on the metaphorical and at the same time technical meaning of ‘rule’ and ‘standard model’ (although kanon is attested only very rarely in Stoic texts, which seem to use kriterion much more frequently, suggesting that kanon is an Epicurean technical term). Kanon thus became associated with the term kriterion, i.e. what allows the action of krinein: ‘to separate’, ‘to distinguish’, and – by extension – ‘to judge’.

Keeping what has just been said in the background, the main purpose of the Project presented here is to study the likely philosophical roots of Epicurean Canonics. The main authors that Epicurus most probably bore in mind as crucial points of reference were Plato and Aristotle – more specifically, the Theaetetus, the De anima, and the Parva naturalia.

As a preliminary remark, it is necessary to make an essential methodological premise: there is no ancient evidence that proves in a certain way Epicurus’ direct acquaintance with the Theaetetus or the De anima (it is much more likely, however, that he knew the Timaeus, as can be deduced especially from Book 14 of On Nature). For this reason, we need to distinguish between 1) a ‘direct’ (or ‘explicit’), and 2) a ‘silent’ (or ‘implicit’) presence (or influence) of Plato, Aristotle, and other philosophers or philosophical traditions we mentioned. By ‘direct’ presence we mean explicit references to Plato and Aristotle in Epicurus’ writings; by ‘silent’ presence we are pointing to the implicit, indirect presence of Aristotle in all those Epicurean texts expounding philosophical doctrines which would appear to imply – or make tacit reference to – the philosophy of Plato and Aristotle. For example, if we limit the investigation to the ‘direct’ presence alone, Epicurus’ reception of Aristotle amounts to almost nothing: the texts by Epicurus where Aristotle’s name appears are very few and not easy to interpret. On the other hand, several Epicurean doctrines are better explained in light of Aristotle, with whom Epicurus often seems to entertain a (simultaneously) polemical and dialectical relationship. The text which has most influenced studies on Aristotle’s influence on the Garden comes from a much-debated Herculaneum Papyrus. We shall briefly recall the salient features of this complex source. The text at issue is part of a letter (probably) by Epicurus, which was preserved by the Epicurean Philodemus in his book Πρὸς τοὺς φασκοβιβλιακούς (Against Those Who Call Themselves Connoisseurs of Books; PHerc. 1005/862, fr. 111 Angeli = 127 Arrighetti = 126F Erbì). It would show Epicurus’ knowledge not only of Aristippus’ treatise On Socrates and Speusippus’ Praise of Plato, but also of Ἀριστοτέ[λους τὰ] Ἀναλυτικὰ καὶ [τὰ Περὶ] φ̣ύσεως, namely the Analytics (whether Prior or Posterior, it is difficult to tell) and Aristotle’s books On Nature (in all likelihood the Physics). On the basis of the title of Philodemus’ work, it can be assumed that Philodemus aims to introduce Epicurus (or the author of the letter) as an authentic connoisseur of books in order to preserve his ‘philosophical credentials’ and exculpate him from the (traditional) charge of ignorance.

As far as Plato and the Theaetetus are concerned, the aim of the Project is to systematically study those parts of the dialogue that may have attracted Epicurus’ attention in the development of his epistemology. It is quite unlikely that Epicurus did not seriously consider the Theaetetus – a text that, given the use which the ancient Stoics made of it, must have circulated widely among the philosophical schools of the Hellenistic period. Before the De anima and the Aristotelian Analytics, this dialogue represented the fundamental text for the debate on knowledge and, more particularly, for the vexatissima quaestio of the relationship between aisthesis and episteme, which constitutes the undisputed foundation of Epicurus’ philosophy. In this sense, the study of the Theaetetus in relation to Epicurus’ epistemology will aim to show how some of the fundamental elements of the Epicurean Canonics were consolidated, developed, and even formed not only in close connection with the philosophy of Leucippus and Democritus, but also through a critical evaluation of the Theaetetus. It is extremely likely that, in order to consolidate his doctrine of the criterion, Epicurus took account of the strong objections to the idea of a close relation between aisthesis and episteme advanced in Plato’s dialogue. The latter was especially relevant with regard to the following issues: 1) the infallibility of sense-perception; 2) the genesis of error; 3) the role of the soul in sense-perception and in cognitive processes; 4) the relationship between sense-perception and memory.

The Timaeus will be considered in close continuity with the Theaetetus and, more generally, with the attention given by the late Plato to perception and the conformation of the sense organs. Indeed, if it is more than plausible that Epicurus knew the Timaeus, it follows that he could not have ignored those sections of the dialogue devoted to the formation of the human body and to perception, particularly vision. We are therefore confident that we will be able to show that the relationship between Epicurus’ epistemology and the Timaeus is deeper that is usually believed. Furthermore, since both the Theaetetus’ and the Timaeus’ theories of perception depend on the notions of ‘symmetry’, ‘efflux’, and ‘pores’, we expect to show that Plato is also a reference point for Epicurus with regard to Empedocles’ alleged empiricism. Before Aristotle, in the Meno Plato testifies that such a theory was defended by Gorgias, who had learned it from Empedocles himself. The philosopher from Akragas was a favourite target of the Epicureans: not only Epicurus himself, but also Colotes and Hermarchus (who wrote a treatise Against Empedocles in 22 books, in addition to one Against Plato and one Against Aristotle).

With regard to Aristotle, we will mainly focus on the De anima, the Posterior Analytics, and certain sections of the Parva naturalia. The Aristotelian part of the research will focus more specifically on sense-perception, understood as both perception and representation. In particular, with a definite advancement compared to the studies published on this topic so far, we intend to examine the complex physiological framework that underlies the Epicurean view of sense-perception. Like Democritus, Epicurus believes that perception and thought occur on the basis of the same physiological mechanism, namely: the motion produced in the sense organ by the impact of atomic structures issuing from the surface of objects, of which they reproduce certain characteristics. Epicurus introduces some important innovations. He explains sense-perception in terms of the dynamis of a specific atomic system, a unitary and composite blend of soul and body which is established via contact with an external stimulus (Epic. Hrdt. 63-64). Epicurus considers simulacra – the atomic films that account for our ability to see and think – as being almost hollow structures, endowed with characteristics that allow them to travel at great speed through media of varying compactness, while maintaining a degree of correspondence with their object (cf. Epic. Nat. 2, Leone 2012). Unlike Aristotle, Epicurus downplays the role of the medium in the case of the perception of distant objects. In addition, Epicurus attaches special importance to the porosity of the structure which receives the sensory stimulus (cf. Epic. Nat. 25 Laursen 1995: 91). He recognizes different levels of homogeneity between simulacrum and object (cf. Hrdt. 51). He admits that the transmission of a perceptual residue to the heart is decisive for the formation of mental representations (Hrdt. 50); he argues that this residue is able to convey only the typological characteristics of the object (cf. Verde 2016). He investigates the origin and nature of perceptual errors, in particular the kind that arises in conjunction with fantastic and dreamlike representations (Nat. 34, col. XV Leone; see Gigandet 2017, Gourinat 2017, Tsouna 2018, and Konstan 2020). In light of this substantial revision, it is plausible to think that Epicurus sought to overcome some difficulties implicit in the Democritean doctrine and to provide a more adequate physiology of sense-perception to ground his epistemology. By adopting a very original interpretive perspective, the present research intends to investigate the reasons for this reconsideration in light of Aristotle’s criticism of his predecessors’ materialistic cognitive theories in the De anima and Parva naturalia (e.g. De sensu et sensibilibus, De insomniis, and De memoria et reminiscentia). More specifically, we will try to show that the Epicurean reworking of the atomistic doctrine of perception is able, on the one hand, to overcome the Aristotelian criticism of the principle that like attracts like – or the principle that sense-perception occurs between materialistically homogeneous entities – and, on the other hand, to account for perceptual errors, without introducing other faculties in addition to perception and thought or undermining the truthfulness of sense-perception.

The concrete possibility of the influence of the Posterior Analytics on the Epicurean notion of science and knowledge will also be investigated, notwithstanding Epicurus’ almost complete rejection of demonstration (cf. Morel 2015). Moreover, again with reference to Epicurean Canonics, the study of some sections of the Posterior Analytics will explore the relationship between sense-perceptions and memory (APo. II 19, 100a3-9), the origin of the concept of hypolepsis (cf. e.g. APo. I 33, 88b37; cf. also De an. III 3, 427b16-17) – which according to Epicurus can be true or false (cf. Diog. Laert. X 34) – and the issue of whether the distinction between nominal and essential definition (APo. II 10) was an important point of reference for the theoretical genesis of prolepsis, the second criterion of Epicurean Canonics.

Theophrastus
Engraving. Veterum illustrium philosophorum, poetarum, rhetorum, et oratorum imagines ex vetuftis nummis, gemmis, hermis, marmoribus, aliisque antiquis monumentis defumptae a Io. Petro Bellorio, Romae 1685, pars prima, 38

The Project aims to broaden the survey to include not only Plato and Aristotle but also other sources equally relevant to Epicurean epistemology. To keep within the Aristotelian school, some studies (Sedley 1998: Ch. 6) have shown Theophrastus to be an important source for Epicurus. Given the restricted focus of the Project, we will examine the specific issue of Theophrastus’ likely influence on the method of multiple explanations (pleonachos tropos) that Epicurus uses to examine the causes of celestial phenomena (ta meteora) in the Letter to Pythocles. It has been argued that Epicurus derived the method of multiple explanations directly from Theophrastus (cf. Podolak 2010): on the basis of the few indirect testimonies on Theophrastus’ meteorological thought and of the so-called Syriac-Arabic Meteorology attributed (albeit not unanimously: see especially the recent Bakker 2016: 145ff.) to this philosopher, we will assess whether and in what terms the alleged Theophrastean use of multiple explanations really influenced Epicurus’ pleonachos tropos, which certainly represents an important and in many ways original part of his epistemology. In the context of this research on Epicurean meteorology and Theophrastus, an important part of the Project will be devoted to examining the very likely Aristotelian roots of many of the explanations of celestial phenomena found in Epicurus’ Letter to Pythocles. This Epicurean letter in all likelihood presupposes a constant engagement not only with the many pre-Socratic philosophical traditions concerning celestial phenomena (known to Epicurus mainly from doxographical texts that can be traced back to the Peripatetic tradition, especially Theophrastus) but also with Aristotle’s Meteorology, not least from a methodological and epistemological point of view.

Diego Velázquez, Democritus
Oil on canvas (circa 1630)
Musée des Beaux-Arts, Rouen

Here the aforementioned Democritus plays a central role: his unitary conception of the soul, identification of the soul with the intellect (68A101 DK), fully materialistic perceptual theory, and distinction between obscure and genuine knowledge certainly had a crucial bearing on Epicurus’ epistemology (and psychology). Therefore, the main goal will be to investigate this influence, also in order to highlight any discontinuities between the Democritean and Epicurean epistemology. In this context, the controversial figure of the Democritean Nausiphanes will be privileged. In order to belittle the originality of Epicurean epistemology, Ariston (cf. Diog. Laert. X 14) – probably the Stoic philosopher – polemically argued that Epicurus had written his Canon by plagiarizing Nausiphanes’ Tripod. This point needs to be investigated and clarified on the basis of the scant information we have about Nausiphanes’ philosophy. Thanks to Sextus Empiricus (M VII 138 = 68B11 DK) we know that Democritus wrote a treatise called Canons; it will be necessary to understand if Democritus’ work had any influence on Nausiphanes’ Tripod and whether – and to what extent – these two texts influenced the contents of Epicurus’ Canon.

One of the objectives of the Project is to further develop the investigation of the polemical relationship between Epicurus and the Pyrrhonian tradition. The trait d’union with this philosophical tradition is still Nausiphanes, who had strong sympathies for Pyrrho’s philosophy (see 75A2 DK). Although there are some rather dated studies on Epicureanism and Scepticism, there is still need to shed light on this polemic waged by Epicurus, and attested by Book 4 of Lucretius’ De rerum natura. The twofold goal will be to understand the identity of these sceptical philosophers and whether this polemic influenced the genesis of Epicurus’ epistemology.

Arcesilaus and Carneades
Cicero’s Academici libri, Lipsiae 1810, title page, detail.

Recently, in an article on Book 34 of Epicurus’ On Nature (Spinelli 2020), it has been hypothesized that the sceptical target of the Epicurean controversy is to be found not in Pyrrho (who was not a Pyrrhonian, which is to say a sceptic in the full sense of the term) or Arcesilaus (especially for chronological reasons), but most likely in Timon of Phlius. Timon can be considered the likely target of some specific arguments presented by Epicurus in this book of On Nature in order to reinforce the crucial value and role of sense-perception for any correct approach to epistemological questions. Our aim is to examine this controversy in a systematic and philologically scrupulous way and to highlight Timon’s role as Epicurus’ direct target. It will also be necessary to determine whether – and, if so, in what way – the controversy involved any of Democritus’ major followers (e.g. Metrodorus of Chios and Nausiphanes), any of the Megarian/Dialectical philosophers attacked by Epicurus in On Nature Book 28, or even Metrodorus of Lampsacus: recently (Corradi 2021) it has been argued that in order to attack the sceptical attitude, Lucretius follows the strategy that Aristotle deploys in Metaphysics Book Γ against those who deny the principle of non-contradiction (and it is not unlikely that this includes the Megarian philosophers).

The Project we are presenting here aims to contribute to our knowledge of Epicureanism and of ancient philosophy more generally. Given the oft-repeated absence of systematic contributions on the sources of Epicurean Canonics, the scope of this Project will constitute a significant step forward in the study of Hellenistic philosophies as well. To this day the question of whether Hellenistic philosophers were really interested in earlier traditions of thought remains somewhat controversial. Our Project intends to shed light on this point and to show, through systematic analyses, that Epicurus’ epistemology would be unthinkable without a constant engagement with Plato, Aristotle, and the other philosophical traditions mentioned here.