Acatalepsy, term which signifies the impossibility that something may be known or understood. See Conception.

This word is formed using the privative α and καταλαμβάνω, discover, seize , which is itself composed from κατὰ and λαμβάνω, to take . See Catalepsy.

Acatalepsy is the synonym of incomprehensibility . See Comprehension.

The Pyrrhonians or Skeptics argued for absolute acatalepsy . According to them, all the sciences or human knowledge were not going to arrive at anything but appearance and likelihood. They decried the senses a great deal, and regarded them as the principle source of our errors and seduction. See Skeptic, Pyrrhonian, Academic, Senses, Error, Probability, Doubt, Suspension, etc.

* Arcesilaus was the first defender of acatalepsy. Here is how he reasoned: we cannot know anything, he said, not even that which Socrates believed to know—that we know nothing.

This impossibility comes about from the nature of things and from the nature of our faculties, but more from the nature of our faculties than of things.

One should neither deny nor affirm anything, because it is unfit for a Philosopher to express approval where one thing may be false or uncertain, and to decide on something before being instructed.

But everything having about the same degrees of probability for and against, a philosopher can therefore declare himself against whoever denies or affirms anything, or whoever is sure of having finally found either the truth that he seeks or new reasons for believing that the truth is not made for us to know. It is thus that Arcesilaus sought the truth all his life, perpetually struggling with the Philosophers of his time.

But if neither the senses nor reason are sure enough guarantees that one will be heard in the schools of philosophy, he added, they suffice at least in the conduct of life, where we risk nothing by following probabilities, since we are among people without better means for determining anything.