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Acatalepsy (from the Greek α̉-, privative, and καταλαμβάνειν, to seize), in philosophy, is incomprehensibleness, or the impossibility of comprehending or conceiving a thing.[1] It is the antithesis of the Stoic doctrine of katalepsis or Apprehension.[2] According to the Stoics, katalepsis was true perception, but to the Pyrrhonists and Academic Skeptics, all perceptions were acataleptic, i.e. bore no conformity to the objects perceived, or, if they did bear any conformity, it could never be known.[2]

For the Academic Skeptics acatalepsy meant that human knowledge never amounts to certainty, but only to probability.[3] For the Pyrrhonists it meant that knowledge was limited to the phantasiai (appearances) and the pathē. 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 Academics responded to the Stoic theory of katalepsis with the following syllogism:

  1. There are true and false impressions (phantasiai).
  2. False impressions are non-kataleptic
  3. True impressions are always such that false impressions could appear identical to them.
  4. Among impressions with no perceptible difference between them, it is impossible for some to be kataleptic and others not.
  5. Therefore, there are no kataleptic impressions.[4]

See alsoEdit


  1. ^ a b   This article incorporates text from a publication now in the public domainChambers, Ephraim, ed. (1728). "article name needed". Cyclopædia, or an Universal Dictionary of Arts and Sciences (first ed.). James and John Knapton, et al.
  2. ^ a b George Henry Lewes, 1863, The biographical history of philosophy, Volume 1, page 297
  3. ^ acatalepsy. (n.d.) Webster's Revised Unabridged Dictionary. (1913). Retrieved February 16 2015
  4. ^ Cicero, Academica 2.40