Katalepsis in the context of "Acatalepsia"

Academic skepticism was the philosophy of the skeptical period of the Academy dating from around 266 BCE, when Arcesilaus became scholarch, until around 90 BCE, when Antiochus of Ascalon rejected skepticism, although individual philosophers, such as Favorinus and his teacher Plutarch, continued to defend skepticism after this date. Unlike the existing school of skepticism, the Pyrrhonists, they maintained that knowledge of things is impossible. Ideas or notions are never true; nevertheless, there are degrees of plausibility, and hence degrees of belief, which allow one to act. The school was characterized by its attacks on the Stoics, particularly their dogma that convincing impressions led to true knowledge. The most important Academics were Arcesilaus, Carneades, and Philo of Larissa. The most extensive ancient source of information about Academic skepticism is Academica, written by the Academic skeptic philosopher Cicero.

In Hellenistic philosophy, phantasiai (φαντασίαι) are pieces of information received from sense experience. The Pyrrhonists, Epicureans, and Stoics use the term to refer to information received through the senses and arising in thoughts.

In Stoicism, the phantasiai represent pre-cognitive judgments originating from our previous experiences or our subconscious thinking. The founder of Stoicism, Zeno of Citium, suggested that the soul is imprinted by the senses much in the same way as a signet ring imprints its shape in soft wax; all psychological states and activities, such as mental assent, cognition, impulse, and knowledge are all either extensions or responses to phantasiai. According to Epictetus, the sage avoids doxa, a weak or false belief, by withholding assent when conditions do not permit a clear and certain grasp of the truth of a matter. Some phantasiai experienced in perceptually ideal circumstances, however, are so clear and distinct that they could only come from a real object; these were said to be kataleptikê (fit to grasp). The kataleptic phantasiai compels assent by its very clarity and represents the criterion of truth.