Of Pitane in Aeolis, 316/5–242/1 bc, head of the Academy from c.269. He introduced scepticism (see sceptics) into Plato's school, thereby founding the ‘New Academy’. He seems to have appealed to the examples of Socrates and Plato. Like Socrates, Arcesilaus would examine or argue against a given thesis and make no assertions of his own. His professed attitude of withholding assent was adopted to avoid error and rashness of judgement.
Arcesilaus' most influential and famous argument was directed against the Stoic theory of knowledge (see stoicism). He argued that given the definition of the Stoic criterion of truth, the so‐called cognitive impression, one could show that nothing could be grasped or apprehended, since it was impossible to find an impression of such a kind that it could not be false. For any true and clear impression one could describe a situation in which an otherwise indistinguishable impression would be false. Since the Stoics held that the wise man would never assent to a false impression, it followed that the Stoic sage must withhold judgement on all matters. To the Stoic objection that suspension of judgement would make action, and hence life, impossible, Arcesilaus replied that it was possible to act without assenting to anything, and that in the absence of certain knowledge a wise man could be guided by ‘what is reasonable’.
The thesis that ‘nothing can be grasped’ has been described as a doctrine of the sceptical Academy, but this is a mistake: Arcesilaus and his successors down to Carneades insisted that they did not know or assert that nothing could be known, any more than they knew or asserted any other philosophical thesis.
Subjects: Classical Studies.