Pyrrho, born in Elis, first proclaimed the principles of Scepticism. He joined Alexander’s army and fought campaigns as far as India. He returned to Elis and died there in 275 BC. Timon was a disciple of Pyrrho and died in 240 BC..
Scepticism of the senses had troubled Greek philosophers for some time. Plato and Parmenides went as far as to deny the cognitive value of perception altogether. Protagoras and other Sophists were led by the apparent ambiguities and contradictions of sense perception into a form of subjectivism, like Hume’s. Pyrrho added moral and logical scepticism, arguing that there could never be a wholly objective rational ground for preferring one course of action to another. One might as well conform to the customs of whatever society one inhabited.
Dogmatic scepticism concludes that nobody knows, and nobody can ever know for sure. If one relies on deductive reasoning, as the Greeks did, then every argument is either circular, or hangs from nothing – there is no original premiss to form the basis.( except as provided by religion).
According to Timon, the phenomenon itself is valid – “Honey tastes sweet” – but it may not actually BE sweet, only appear so. This idea was followed in Hume’s approach to causality. One cannot infer what one has not seen – ie inferred causality without an observed mechanism. But if phenomena are observed frequently together, it was accepted that one can infer one from the other.
The Sceptics doctrine was taken up by the Academy in Athens, until 69 BC, when it followed the Stoic doctrine. For 200 years it focused on refuting any thesis proposed, but did not put forward its own. Eg in 156 BC Carneades visited Rome and gave a lecture on Aristotle and Plato’s Justice, which was very well received. The next day he gave a another lecture refuting all that he said before – very confusing to the Romans.
The next leader of the Sceptics, Clitomachus, wrote 400 books, refuting divination, magic, astrology etc. He expounded probability – nothing is certain, but some things are more certain than others.