All Sense-Perceptions Are True: Epicurean Responses to Skepticism and Relativism

  • Katja Maria Vogt
Part of the The New Antiquity book series (NANT)


Epicurean epistemology is infamous for the claim that all sense-perceptions are true.1 This is how Lucretius puts it: what is perceived by any of the senses at any given time is true (De Rerum Natura [DRN] 4.499). This claim—which I shall call SPT—seems deeply misguided. It appears obvious that sense-perception can err. The plan for this chapter is to show that SPT is a sophisticated philosophical proposal and, what is more, a proposal that aims to capture the truth in relativism.2


Sense Perception Representational State Criterial Argument Parity Argument Atomic Image 
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  1. 1.
    Important discussions of this claim include Gisela Striker, “Epicurus on the Truth of Sense-Impressions,” Archiv für Geschichte der Philosophie 59 (1977): 125–42, reprinted in Gisela Striker, Essays in Hellenistic Epistemology and Ethics (Cambridge: Cambridge University Press, 1996), 77–91; David Sedley, Lucretius and the Transformation of Greek Wisdom (Cambridge: Cambridge University Press, 1998); Elisabeth Asmis, Epicurus’ Scientific Method (Cornell: Cornell University Press, 1984) and Elisabeth Asmis, “Epicurean Empiricism,” in The Cambridge Companion to Epicureanism, ed. James Warren (Cambridge: Cambridge University Press, 2009), 84–104; David K. Glidden, “‘Sensus’ and Sense Perception in the ‘De rerum natura,’” California Studies in Classical Antiquity 12 (1979): 155–81; James Warren, “Lucretius and Greek Philosophy,” in The Cambridge Companion to Lucretius, ed. Stuart Gillespie and Phillip Hardie (Cambridge: Cambridge University Press, 2007), 19–32; Stephen Everson, “Epicurus on the Truth of the Senses,” in Epistemology, ed. Stephen Everson (Cambridge: Cambridge University Press, 1990), 161–83; Fritz Jürss, Die epikureische Erkenntnistheorie (Berlin: Akademie-Verlag, 1991); C. C. W. Taylor, “‘All Perceptions Are True,’” in Doubt and Dogmatism, ed. Malcolm Schofield et al. (Oxford: Oxford University Press, 1980), 105–24; Paul Vander Waerdt, “Colotes and the Epicurean Refutation of Skepticism,” Greek, Roman and Byzantine Studies 30 (1989): 225–67.CrossRefGoogle Scholar
  2. 4.
    I agree with David Sedley’s outline of the sections of Book 4 (Sedley, Lucretius, 150); 26–238: existence and mobility of images; 239–468: vision, truth, and falsity; 469–521: refutation of skepticism; 522–721: the other senses; 722–822: thought; 823–57: critique of teleology; 858–1287: nutrition, motion, sleep, dreams, sex. For the Latin text, see Lucretius, De Rerum Natura, 3 vols., Books 1–4, commentary by Cyril Bailey (Oxford: Oxford University Press, 1947). All translations, unless otherwise noted, are my own.Google Scholar
  3. 5.
    It is so obviously problematic that it was already improved upon by the Pre-Socratic Metrodorus of Chios, a student of Democritus. Metrodorus says at the beginning of his book On Nature: “None of us knows anything, not even this, whether we know or we do not know; nor do we know what ‘to not know’ or ‘to know’ are, nor on the whole, whether anything is or is not” (Cicero, Acad. 2.73, trans. Mi-Kyoung Lee, “Antecedents in Early Greek Philosophy,” in The Cambridge Companion to Ancient Scepticism, ed. Richard Bett (Cambridge: Cambridge University Press, 2010), 13–35, 19 = DK 70B1 [H. Diels, and W. Kranz, eds., Die Fragmente der Vorsokratiker, 3 vols. (Berlin: Weidmann, 1996). [= DK; hereafter cited as DK]; SE M 7.48, 87–88 [Sextus Empiricus: Against the Logicians, ed. and trans. R. Bett (Cambridge: Cambridge University Press, 2005). [=SE; hereafter cited as SE or Sextus]; Eusebius, Praep. evang. 14.19.9 [Eusebius Werke, Band 8: Die Praeparatio evangelica, ed. K. Mras. Die griechischen christlichen Schriftsteller, vols. 43.1 and 43.2 (Berlin: Akademie Verlag, 1954 [43.1], 1956 [43.2]).CrossRefGoogle Scholar
  4. 7.
    “You will find that by the senses was first created / the notion of truth; and that the senses cannot be refuted.” [Invenies primis ab sensibus esse creatam / notitiam veri neque sensus posse refelli.] (478–79); notitiam veri is ambiguous: it could mean “notion of truth” or “acquaintance with truth.” The context suggests that Lucretius wants to cover both ideas. This argument is in line with what appears to be an Epicurean argument against skepticism, namely, the charge that skeptics cannot have concepts and accordingly cannot think. Cf. Katja Maria Vogt, “Skepticism and Concepts: Can the Skeptic Think?,” Chapter 6 in K. M. Vogt, Belief and Truth: A Skeptic Reading of Plato (New York: Oxford University Press, 2012), 140–57.CrossRefGoogle Scholar
  5. 10.
    Cf. Epicurus’s defense of the truth of sense-perceptions: “All sensation, he says, is arational and does not accommodate memory … Nor does there exist that which can refute sensations: neither can like sense refute like, because of their equal validity nor unlike unlike, since they are not discriminatory of the same things; nor can reason, since all reason depends on the senses; nor can one individual sensation refute another, since they all command our attention. And also the fact of sensory recognitions confirms the truth of sensations. And our seeing and hearing are facts, just as having pain is … The figments of madmen and dreaming are true. For they cause movement, whereas the non-existent does not move anything”] (DL 10.31–32 [Diogenes Laertius, Lives of Eminent Philosophers, with an English translation by R. D. Hicks, 2 vols. (Cambridge, MA: Harvard University Press; London: Wm. Heinemann, 1958–59); vol. 1, 1959 [=DL; hereafter cited as DL]; trans. LS 16B [A. A. Long, and D. N. Sedley, eds. and trans., The Hellenistic Philosophers, 2 vols. (Cambridge: Cambridge University Press, 1987) [=LS; hereafter cited as LS].Google Scholar
  6. 13.
    Lucretius uses the same word, sensus, for sense-perception in general, for senseorgans (physiologically conceived), and for their deliverances (the perceptions); cf. Glidden, “‘Sensus’ and Sense Perception,” 155. Accordingly, it is not always evident that “all sense-perceptions are true” and “the senses are truthful” are two theses—but they are. It is likely that Epicurus can be credited with the view that the senses never lie (Lucullus 26.82; Cicero, Akademische Abhandlungen Lucullus, ed. and trans. Christoph Schäublin [Hamburg: Felix Meiner Verlag, 1998]). Moreover, it is likely that Epicurus took that claim to be immediately related to another claim, one that is rather close to SPT, namely, that if one perception were false, then none would be true. According to Cicero, Epicurus says, for this reason, that all of the senses give a “true report” (De natura Deorum 1.25, 70). Cicero, De Natura Deorum. Academica, with an English translation by H. Rackham (London: William Heinemann, 1933).Google Scholar
  7. 15.
    Plato: Complete Works, ed. John M. Cooper (Indianapolis, IN: Hackett, 1997).Google Scholar
  8. 16.
    Cf. Michael Frede, “Observations on Perception in Plato’s Later Dialogues,” and John Cooper, “Plato on Sense-Perception and Knowledge (Theaetetus 184–86),” both in Plato 1: Metaphysics and Epistemology, ed. Gail Fine (Oxford: Oxford University Press, 1999), 355–76 and 377–83.Google Scholar
  9. 20.
    Epicurus was firmly committed to this view. Cf. DL 10.32 [= LS 15F] and Plutarch adv. Col. 1109B; 1121 D, E; 1124 B. Plutarch, Reply to Colotes in Defense of the Other Philosophers, in Plutarch: Moralia, vol. 14, trans. Benedict Einarson and Phillip H. de Lacy (Cambridge, MA: Harvard University Press, 1967), 151–315.Google Scholar
  10. 25.
    Rist argues that “a real event takes place in the act of sensing” (John M. Rist, Epicurus: An Introduction [Cambridge: Cambridge University Press, 1972], 19–20). Striker, “Epicurus on the Truth of Sense-Impressions,” says that the interpretation that “true” means “real” is, at the time, the standard view in the literature.Google Scholar
  11. 30.
    Today, many philosophers assume that, while perceptual experience is non-factive, perception is factive. Cf. Tim Crane: “I assume the now standard terminological distinction between perceptual experience, which is non-factive or non-relational, and perception, which is both factive and relational.” (“Is Perception a Propositional Attitude?,” The Philosophical Quarterly 59 [2009]: 452–69.)CrossRefGoogle Scholar

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© Katja Maria Vogt 2016

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  • Katja Maria Vogt

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