Philosophical movement which dominated Plato’s Academy from the 3rd century until the beginning of the 1st century BC. Its main target was the dialectical elenchus of philosophical theories and theses. Its best known arguments attacked the thesis that knowledge, considered to be necessary for a rational and happy life, is attainable.

Reference of the term

As soon as Arcecilaus became the head (scholarch) of the Academy in the second quarter of the 3rd c., Academy entered a distinct period of its history during which it developed a sceptical philosophy. The Academic philosophers of this period (which extends until the beginning of the 1st century BC) were called Ἀκαδημαϊκοί, not Σκεπτικοί. Nevertheless, already in late antiquity the Academics were occasionally called ‘Sceptics’. Modern scholars have adopted the term ‘Academic Sceptics,’ thus acknowledging a significant similarity between the Academics and the Pyrrhoneans. The Pyrrhoneans called themselves Σκεπτικοί (σκέψις = inquiry), in order to underline their devotion to, and persistence in, philosophical investigation. According to their view, philosophical investigation had not managed to reach any truth, and because of that they did not adopt any philosophical thesis or theory, not even the thesis that truth and certain knowledge are impossible– which is precisely the thesis that we standardly connect with scepticism nowadays. The belief that attaining knowledge is impossible was only adopted by a few late Academics (such as Philo of Larissa). However, it is this late version of Academic Scepticism that Cicero represents in the Academica and Augustine attacks in his Contra Academicos. Both these works formed the modern perception of Scepticism. Thus, the original sense of the term, which depicted the philosophical stance of the most prominent Academic Sceptics, got overshadowed.

The most important Academic Sceptics, method and sources

Arcesilaus (316/5-241/0 BC) and Carneades (214/3 – 129/8 BC) are the most prominent Academic Sceptics.

Arcesilaus, head of the Academy for about 25 years, turned the Academy to Scepticism, invoking the Socratic elenchus as we find it in the early Platonic dialogues. Socrates was leading his interlocutors to ἀπορία (=perplexity or puzzlement), i.e. to a state in which they could not rationally either maintain their initial thesis or adopt the opposite one. In an analogous way, Arcesilaus tested philosophical theses in order to show that the philosophers who held them were not legitimated to adopt either these theses or the opposite ones. The arguments used in this test are dialectical, i.e. they are based on premises adopted, or at least not rejected, by the philosopher who holds these theses. Consequently, insofar as Arcesilaus mobilizes dialectical arguments, he is committed neither to the premises nor to the conclusions of his arguments.

Carneades, head of the Academy and one of the most prominent philosophers of 2nd c. BC, philosophized in the same dialectical spirit and became famous for arguing on both sides of a question. However, he did not confine himself to arguing just against theses actually held by other philosophers: he also used to explore systematically different possible theses on philosophical problems.

Following the Socratic example both Arcesilaus and Carneades wrote nothing. Clitomachus (Carneades’ student and successor as head of the Academy) became a prolific writer in his attempt to interpret his teacher’s thought, but none of his works has survived. Thus, our main sources on Academic Scepticism are Cicero’s Academica and Sextus’ Against the professors VII, both written by authors who were embracing varieties of ancient scepticism different from the version developed by the two great Academic Sceptics.

Academic Sceptics against the Stoic theory of knowledge

Academic Sceptics’ main opponents were the Stoics, and the principal target of the best known Academic arguments was the Stoic theory of knowledge.

The Stoics distinguished a particular class of perceptual impressions, the cognitive impressions. These impressions, besides being true, they are also recognizable as such, because they shed light to their objects and present them, and themselves, to us so evidently that they ‘lay hold of us almost by the hair and drag us off to assent’ . Thus we get a criterion of truth, which provides, at least for the Stoic sage, an unshakable foundation of knowledge. Contrary to what we all normally do, the Stoic sage gives his assent only to cognitive impressions, and to what follows with logical necessity from them, thus never forming mere belief (δόξα). This is very important because, according to the Stoics, even the slightest false belief may gradually cause the whole edifice of wisdom to collapse. Therefore, what makes the Stoic sage a sage is his infallibility rather than the extended width of his knowledge.

The Academic Sceptics initially attempted to show that there are not any cognitive impressions. Using examples of indistinguishable objects, such as identical twins, they showed that for every impression that is true, there is an indistinguishable impression which is false; and using cases of madness, drunkenness, dreaming and perceptual illusions, they showed that there are no impressions affecting our minds in such a way that enables us infallibly to distinguish them as cognitive.

But if there are no cognitive impressions, then everything is inapprehensible (ἀκατάληπτα) and, therefore, as Arcesilaus argues, the Stoic sage, in order to be infallible, has to suspend assent universally (i.e. arrive at universal ἐποχή). Carneades, on the other hand, chose to argue for the conclusion that, if everything is inapprehensible, then it is necessary sometimes, even for the sage, to form beliefs.

A criterion for the conduct of life

The Stoics defended cognitive impressions by claiming that this kind of impressions is a prerequisite and essential constituent of wisdom, and they counterattacked the Sceptics by the inactivity (apraxia) objection: the sceptical arguments render the ideal of a wise and happy life impossible, and they tend to render impossible even ordinary everyday actions.

The Academics answered this objection by arguing that what is needed for a rational and happy life is not necessarily based on what is true and infallible. Arcesilaus argued that ‘the reasonable’ (τὸ εὔλογον) is enough, since right actions are those someone has a reasonable justification for, and happiness and prudence reside in these actions. Carneades argued that persuasive impressions (πιθαναὶ φαντασίαι) are sufficient for the conduct of life. Depending on the situation, we check the persuasive impressions in their connection to one another and to the conditions in which they arose; we then follow those that seem to us to be true, i.e. the more convincing ones, although our being convinced neither makes them actually true nor renders them more probably true. Thus, according to Carneades, acting rationally does not entail being infallible: the existence of cognitive impressions and the Stoic ideal of wisdom are not inescapable for someone aiming at a rational and happy life.

Divergent interpretations

Already in antiquity and also among modern scholars, we find divergent and contradictory interpretations both of Arcesilaus’ and of Carneades’ philosophy, according as their arguments are understood as totally dialectical or as leading to theses they are themselves committed to. For example, there are interpretations proposing that universal ἐποχή was not just a state the Stoic sage was confronted with, but it was an ideal that Arcesilaus was himself committed to, as it forms part of his positive contribution to the philosophical discussion. However, most of modern interpretations converge on a dialectical or Socratic interpretation of Arcesilaus’ philosophical stance.

In antiquity, Carneades’ pupils developed equally contradictory interpretations. Metrodorus and Philo of Larissa attributed to Carneades a mitigated scepticism maintaining that their teacher actually adopted the thesis that the sage can form beliefs, and that therefore it was Carneades’ view that the Sceptic can have beliefs. On the other hand, Clitomachus argued that Carneades was not committed to this thesis, since his relevant argument was of a merely dialectical character. Modern scholars are similarly divided: some propose a totally dialectical interpretation of Carneades’ views, while others maintain that the theory of persuasive impressions commits Carneades to a fallibilist epistemological thesis .

The discussion about the two great Academics remains open.


In antiquity, the Academics’ dialectical arsenal came to the Pyrrhoneans who developed a new sceptical philosophy, outside the Academy, in the 1st c. BC. In the modern era, arguments of the Academics, as they are preserved in Sextus and Cicero, influenced modern philosophers (Descartes, Montaigne, Hume), had a significant effect on epistemological discussions, and led to the growth of modern scepticism.

Author: Anna Tigani
  • Allen, J. "Carneades." Zalta, E.N ed. The Stanford Encyclopedia of Philosophy .. 2012.
  • Brittain, Ch. "Arcesilaus." Zalta, E.N ed. The Stanford Encyclopedia of Philosophy 2008 .
  • Frede, M. "The Sceptics." Furley, D. J. ed. Routledge History of Philosophy 2: From Aristotle to Augustine. 1999.
  • Bett, R. ed. The Cambridge Companion to Ancient Scepticism. Cambridge University Press, 2010.
Middle Platonism

Middle Platonism

Period of Platonist philosophy extending from 1st c. BCE to...

Antiochus of Ascalon

Antiochus of Ascalon

Platonist philosopher (ca. 130-68 BCE), pupil of the...

The Atlantis myth

The Atlantis myth

The most famous Platonic myth. It is included in the...

Plato and the sciences of his time

Plato and the sciences of his time

Plato, during the fifty years he was active as an author,...