Porphyry (philosopher) in the context of "Porphyrian tree"

Neoplatonism is a version of Platonic philosophy that emerged in the 3rd century AD against the background of Hellenistic philosophy and religion. The term does not encapsulate a set of distinct ideas based on a form of Platonism as much as a series of Platonic thinkers coming primarily from a certain ancient historical period. Among the common ideas it maintains is monism, the doctrine that all of reality can be derived from a single principle, "the One".

Neoplatonism began with Ammonius Saccas and his student Plotinus (c. AD 205 – 271) and stretched to the sixth century. After Plotinus there were three distinct periods in the history of Neoplatonism: the work of his student Porphyry (third to early fourth century); that of Iamblichus (third to fourth century); and the period in the fifth and sixth centuries, when the academies in Alexandria and Athens flourished.

Criticism of Christianity has a long history that stretches back to the initial formation of the religion in the Roman Empire. Critics have challenged Christian beliefs and teachings, as well as actions taken in the name of the faith, from the Crusades to modern terrorism. The arguments against Christianity include claims that it is a faith of violence, corruption, superstition, polytheism, homophobia, bigotry, pontification, abuses of women's rights, and sectarianism.

In the early years of Christianity, the Neoplatonic philosopher Porphyry emerged as one of the major critics with his book Against the Christians, along with other writers like Celsus and Julian. Porphyry argued that Christianity was based on false prophecies that had not yet materialized. Following the adoption of Christianity by the Roman Empire, dissenting religious voices were gradually suppressed by both governmental and ecclesiastical authorities. Christianity has faced significant theological criticism from thinkers of other Abrahamic religions, particularly including Judaism and Islam. Notably, Maimonides, the renowned rabbi, Jewish philosopher, and Torah scholar of the 12th century, argued that Christian practices and doctrines constituted idolatry and deviated from the strict monotheism (shituf) of Jewish and Muslim theologies. Similarly, Islamic scholars have critiqued Christian beliefs about the Trinity and the divinity of Jesus, viewing these concepts as incompatible with the concept of monotheism. These critiques reflect deep theological disagreements rooted in their shared scriptural traditions and divergent doctrinal interpretations. A millennium later, the Protestant Reformation led to a fundamental split in European Christianity and rekindled critical voices about the Christian faith, both internally and externally. In the 18th century, deist philosophers such as Voltaire and Jean-Jacques Rousseau were critical of Christianity as a revealed religion. With the Age of Enlightenment, Christianity was criticized by major thinkers and philosophers, such as David Hume, Thomas Paine, and the Baron d'Holbach. The central theme of these critiques sought to negate the historical accuracy of the Christian Bible and focused on the perceived corruption of Christian religious authorities. Other thinkers, like Immanuel Kant, offered critiques of traditional arguments for the existence of God, while professing to defend Christian theology on novel grounds.

Pythagoreanism originated in the 6th century BC, based on and around the teachings and beliefs held by Pythagoras and his followers, the Pythagoreans. Pythagoras established the first Pythagorean community in the ancient Greek colony of Kroton, in modern Calabria (Italy) circa 530 BC. Early Pythagorean communities spread throughout Magna Graecia.

Already during Pythagoras's life it is likely that the distinction between the akousmatikoi ("those who listen"), who is conventionally regarded as more concerned with religious, and ritual elements, and associated with the oral tradition, and the mathematikoi ("those who learn") existed. The ancient biographers of Pythagoras, Iamblichus (c. 245 – c. AD 325) and his master Porphyry (c. 234 – c. AD 305) seem to make the distinction of the two as that of 'beginner' and 'advanced'. As the Pythagorean cenobites practiced an esoteric path, like the mystery schools of antiquity, the adherents, akousmatikoi, following initiation became mathematikoi. It is wrong to say that the Pythagoreans were superseded by the Cynics in the 4th century BC, but it seems to be a distinction mark of the Cynics to disregard the hierarchy and protocol, ways of initiatory proceedings significant for the Pythagorean community; subsequently did the Greek philosophical traditions become more diverse. The Platonic Academy was arguably a Pythagorean cenobitic institution, outside the city walls of Athens in the 4th century BC. As a sacred grove dedicated to Athena, and Hecademos (Academos). The academy, the sacred grove of Academos, may have existed, as the contemporaries seem to have believed, since the Bronze Age, even pre-existing the Trojan War. Yet according to Plutarch it was the Athenian strategos (general) Kimon Milkiadou (c. 510 – c. 450 BC) who converted this, "waterless and arid spot into a well watered grove, which he provided with clear running-tracks and shady walks". Plato lived almost a hundred years later, circa 427 to 348 BC. On the other hand, it seems likely that this was a part of the re-building of Athens led by Kimon Milkiadou and Themistocles, following the Achaemenid destruction of Athens in 480–479 BC during the war with Persia. Kimon is at least associated with the building of the southern Wall of Themistocles, the city walls of ancient Athens. It seems likely that the Athenians saw this as a rejuvenation of the sacred grove of Academos.

Plotinus (/plɒˈtaɪnəs/; Ancient Greek: Πλωτῖνος, Plōtînos; c. 204/5 – 270 CE) was a hellenised Egyptian Platonist philosopher, born and raised in Roman Egypt. Plotinus is regarded by modern scholarship as the founder of Neoplatonism. His teacher was the self-taught philosopher Ammonius Saccas, who belonged to the Platonic tradition. Historians of the 19th century invented the term "neoplatonism" and applied it to refer to Plotinus and his philosophy, which was vastly influential during late antiquity, the Middle Ages, and the Renaissance. Much of the biographical information about Plotinus comes from Porphyry's preface to his edition of Plotinus' most notable literary work, The Enneads. In his metaphysical writings, Plotinus described three fundamental principles: the One, the Intellect, and the Soul. His works have inspired centuries of pagan, Jewish, Christian, Gnostic, and early Islamic metaphysicians and mystics, including developing precepts that influence mainstream theological concepts within religions, such as his work on duality of the One in two metaphysical states.

Against the Christians (Ancient Greek: Κατὰ Χριστιανῶν; Adversus Christianos) is a late 3rd-century book written by Roman-Phoenician Neoplatonic philosopher Porphyry of Tyre, challenging the writings of Christian philosophers and theologians. Due to widespread censorship by Roman imperial authorities, no known copies of this book exist. Only through references to it in Christian writings criticizing it can its contents be reconstructed.