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Agrippa (c. 50 BCE–c. 150 CE)

(c. 50 BCEc. 150 CE)

Agrippa is known by way of one citation in Diogenes Laertius's Lives of the Philosophers (DL 9.88). Nothing is known of his life, and little of his dates (he lived between the mid-first century BCE and the second century CE). Yet Agrippa is indisputably a figure of the highest importance in the history of skepticism, indeed of epistemology in general. The citation attributes to him the invention (or at least the codification) of five "Modes," or argument patterns, which represent a new methodological rigor and self-consciousness in the development of Pyrrhonian skepticism. Earlier skeptics such as Aenesidemus had presented certain aspects of skeptical procedure in a more or less organized fashion; but the Ten Modes attributed to him are arranged according to the subject matter of the considerations appealed to. By contrast, the Modes of Agrippa seek to categorize skeptical practice according to the type and function of the argument patterns involved.

The Five Modes are summarized in two sources; in addition to Diogenes's brief notice (DL 9.8889), a somewhat longer treatment survives (although without mentioning Agrippa by name) in Sextus Empiricus's Outlines of Pyrrhonism (PH 1.164177). Taken together, they offer a general strategy for inducing doubt (and suspension of judgement, epochē ) on every contentious issue. Two of the Modes, the First and the Third, may be described as material. The First Mode notes, in standard Pyrrhonian fashion, that most important issues are matters of dispute (diaphōnia ) and if they are not, the skeptic will make them so. Sextus Empiricus describes skepticism as "a capacity for opposing appearances to appearances and judgments to judgments in whatever manner, so that we are brought first to epochē and then to tranquility" (PH 1.8). Thus "we find an irresoluble conflict both among lay people and philosophers," which leads to these conditions "since we are unable either to assent or deny" (PH 1.165, cf. DL 9.88). The disputes are said to be "irresoluble" (PH 1.98, 212), because (skeptics allege) no independent criterion of judgment is available for them. Unpacking this claim involves invoking the other three, formal, Modes. This is because, as the Third Mode from Relativity holds, things are never apprehended in themselves and unalloyed, but only "along with something else" (DL 9.89): "the underlying object appears thus and so in relation to the one judging and concomitant circumstances, so we suspend judgment as to its real nature" (PH 1.167). Such considerations form the material for the Ten Modes of Aenesidemus, and via René Descartes and others came to dominate the landscape of epistemological scepticism (e.g., lights seem bright in the dark but dim in sunlight; oars seem straight in air, but bent in water: PH 1.119). Thus people can say how things appear to them but they have no grounds for any pronouncements as to how things really are.

But it is in the exposition and deployment of the three formal Modes that the power and originality of Agrippan skepticism becomes manifest. The Second is that from Regress: "what is adduced as confirmation for what is posited itself requires further confirmation, and that another, and so on ad infinitum " (PH 1.166). The Fourth is the Mode of Hypothesis, which the Dogmatists (Sextus's generic term for his nonskeptical opponents) resort to "when being forced to regress ad infinitum, take as an axiom something which they have not established, but see fit to assume as agreed without demonstration" (PH 1.168). This is hopeless, as Diogenes points out, because there is as a matter of fact no such agreement (DL 9.89). Finally the Fifth Mode, of Circularity, claims that "what ought to support the matter under investigation itself requires confirmation from that very matter" (PH 1.169). Diogenes adds an example: "as for instance someone seeking to confirm the existence of pores [in the skin] on the grounds of the emanations should establish the latter on the basis of the former" (DL 9.89).

The Modes lend themselves to use in combination. Take any dogmatic proposition p : one may ask what it is supposed to rest on. If the answer is "nothing," then it is a mere hypothesis, unworthy of credence by the Fourth Mode. If it is alleged to rest on q, one may ask the same question of q. If one gets the same answer, the same response applies. If q is said to rest on p, then the Mode of Circularity comes in; or else the process goes on, potentially ad infinitum in line with the Second Mode (PH 169174). Credit for seeing the force of such objections is not due to Agrippa. Aristotle was aware of them (Posterior Analytics 1.3 [Barnes, ed. 1984]), and realized that any foundationalist epistemology requires its basic propositions to be more than mere assumptions. But how that is to be doneif it is to be done at allis still a matter of dispute, apparently undecidable. Agrippa fashioned a powerful and elegant arsenal of skepticism, and all modern nonskeptical epistemologies sooner or later must confront them, and the challenge they pose, in one form or another.

See also Aenesidemus; Ancient Skepticism; Sextus Empiricus.


Annas, Julia, and Jonathan Barnes, eds. Outline of Scepticism. Translation of Sextus Empiricus's Outlines of Pyrrhonism. Cambridge, U.K.: Cambridge University Press, 1994.

Barnes, Jonathan. The Toils of Scepticism. Cambridge, U.K.: Cambridge University Press, 1989.

Barnes, Jonathan, ed. The Complete Works of Aristotle. 2 vols. Princeton, NJ: Princeton University Press, 1984.

Hankinson, R. J. The Skeptics. London: Routledge, 1995.

Hicks, R. D., ed. and trans. Diogenes Laertius: Lives of the Eminent Philosophers. 2 vols. Cambridge MA: Harvard University Press, 1925.

R. J. Hankinson (2005)

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