Sextus Empiricus in the context of "Physical phenomena"

A phenomenon (pl. phenomena), sometimes spelled phaenomenon, is an observable event. The term came into its modern philosophical usage through Immanuel Kant, who contrasted it with the noumenon, which cannot be directly observed. Kant was heavily influenced by Gottfried Wilhelm Leibniz in this part of his philosophy, in which phenomenon and noumenon serve as interrelated technical terms. Far predating this, the ancient Greek Pyrrhonist philosopher Sextus Empiricus also used phenomenon and noumenon as interrelated technical terms.

Pyrrhonism is an Ancient Greek school of philosophical skepticism which rejects dogma and advocates the suspension of judgement over the truth of all beliefs. It was founded by Aenesidemus in the first century BCE, and said to have been inspired by the teachings of Pyrrho and Timon of Phlius in the fourth century BCE.

Pyrrhonism is best known today through the surviving works of Sextus Empiricus, writing in the late second century or early third century CE. The publication of Sextus' works in the Renaissance ignited a revival of interest in Skepticism and played a major role in Reformation thought and the development of early modern philosophy.

Carneades (/kɑːrˈniːədiːz/; Greek: Καρνεάδης, Karneadēs, "of Carnea"; 214/3–129/8 BC) was a Greek philosopher, perhaps the most prominent head of the Skeptical Academy in Ancient Greece. He was born in Cyrene. By the year 159 BC, he had begun to attack many previous dogmatic doctrines, especially Stoicism and even the Epicureans, whom previous skeptics had spared.

As scholarch (leader) of the Academy, he was one of three philosophers sent to Rome in 155 BC where his lectures on the uncertainty of justice caused consternation among leading politicians. He left no writings. His ideas were passed on to us through his successor Clitomachus whose own books were lost but relayed to us indirectly in the writings of Cicero and Sextus Empiricus. He seems to have doubted the ability not just of the senses but of reason too in acquiring truth. His skepticism was, however, moderated by the belief that we can, nevertheless, ascertain probabilities (not in the sense of statistical probability, but in the sense of persuasiveness) of truth, to enable us to act.

Richard Henry Popkin (December 27, 1923 – April 14, 2005) was an American academic philosopher who specialized in the history of enlightenment philosophy and early modern anti-dogmatism. His 1960 work The History of Scepticism from Erasmus to Descartes introduced one previously unrecognized influence on Western thought in the seventeenth century, the Pyrrhonian Scepticism of Sextus Empiricus. Popkin also was an internationally acclaimed scholar on Christian millenarianism and Jewish messianism.

Moral skepticism (or moral scepticism in British English) is a class of meta-ethical theories all members of which entail that no one has any moral knowledge. Many moral skeptics also make the modal claim that moral knowledge is impossible. Moral skepticism is particularly opposed to moral realism, the view that there are knowable and objective moral truths.

Some defenders of moral skepticism include Pyrrho, Aenesidemus, Sextus Empiricus, David Hume, J. L. Mackie (1977), Friedrich Nietzsche, Richard Joyce (2001), Joshua Greene, Richard Garner, Walter Sinnott-Armstrong (2006b), and James Flynn. Strictly speaking, Gilbert Harman (1975) argues in favor of a kind of moral relativism, not moral skepticism. However, he has influenced some contemporary moral skeptics.