Acatalepsy

In philosophy, acatalepsy (from the Greek ἀκαταληψία "inability to comprehend" from alpha privative and καταλαμβάνειν, "to seize") is incomprehensibleness, or the impossibility of comprehending or conceiving a thing.^[1] It is the antithesis of the Stoic doctrine of katalepsis (i.e., the ability to apprehend).^[2] According to the Stoics, katalepsis was true perception, but to the Pyrrhonists and Academic Skeptics, no perception could be known to be true. All perceptions were thus acataleptic, i.e. what, if any, conformity between the object and the perception of that object was unknown and, for the Academic Skeptics, could never be known.^[2]

For the Academic Skeptics, acatalepsy meant that human knowledge never amounts to certainty, but only to plausibility. For the Pyrrhonists it meant that knowledge was limited to the phantasiai (typically translated as "appearances," meaning a person's sensed experience) and the pathē (one's feelings). The Pyrrhonists attempted to show, while Academic Skeptics asserted, an absolute acatalepsia; all human science or knowledge, according to them, went no further than to appearances and verisimilitude.^[1]

The Academic Skeptics responded to the Stoic doctrine of katalepsis with the following syllogism:

There are true and false impressions (phantasiai)
False impressions are non-kataleptic
True impressions are always such that false impressions could appear identical to them
Among impressions with no perceptible difference between them, it is impossible for some to be kataleptic and others not
Therefore, there are no kataleptic impressions^[3]

Notes

^ ^a ^b One or more of the preceding sentences incorporates text from a publication now in the public domain: Chambers, Ephraim, ed. (1728). "Acatalepsia". Cyclopædia, or an Universal Dictionary of Arts and Sciences (1st ed.). James and John Knapton, et al.
^ ^a ^b George Henry Lewes, 1863, The biographical history of philosophy, Volume 1, page 297
^ Cicero, Academica 2.40

[cyclopaedia-1] One or more of the preceding sentences incorporates text from a publication now in the public domain: Chambers, Ephraim, ed. (1728). "Acatalepsia". Cyclopædia, or an Universal Dictionary of Arts and Sciences (1st ed.). James and John Knapton, et al.

[lewes-2] George Henry Lewes, 1863, The biographical history of philosophy, Volume 1, page 297

[3] Cicero, Academica 2.40

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v t e Skepticism
Types of skepticism	Philosophical Radical Local Moral Scientific Religious
Skeptical philosophies	Academic Skepticism Ajñana Cartesian Charvaka Humeanism Pyrrhonism Solipsism
Skeptical philosophers	Pyrrho Timon Arcesilaus Lacydes Carneades Clitomachus Philo of Larissa Cicero Aenesidemus Agrippa Sextus Empiricus Montaigne René Descartes David Hume
Skeptical scenarios	Acatalepsy Brain in a vat Dream argument Evil genius Five-minute hypothesis Münchhausen trilemma Problem of the criterion Problem of induction Simulation hypothesis Wax argument
Responses	Here is one hand Semantic externalism Process reliabilism Epistemic closure Contextualism Relativism
Lists	List of books about skepticism List of scientific skeptics List of skeptical conferences List of skeptical magazines List of skeptical organizations List of skeptical podcasts

See also

Notes