Neoplatonism is a version of Platonic philosophy that emerged in the 3rd century AD against the background of Hellenistic philosophy and religion.[note 1][note 2] The term does not encapsulate a set of ideas as much as a series of thinkers. 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. 204/5–271 AD) and stretched to the 6th century AD. After Plotinus there were three distinct periods in the history of neoplatonism: the work of his student Porphyry (3rd to early 4th century); that of Iamblichus (3rd to 4th century); and the period in the 5th and 6th centuries, when the Academies in Alexandria and Athens flourished.
Neoplatonism had an enduring influence on the subsequent history of Western philosophy and religion. In the Middle Ages, neoplatonic ideas were studied and discussed by Christian, Jewish, and Muslim thinkers. In the Islamic cultural sphere, neoplatonic texts were available in Arabic and Persian translations, and notable philosophers such as al-Farabi, Solomon ibn Gabirol (Avicebron), Avicenna (Ibn Sina), and Moses Maimonides incorporated neoplatonic elements into their own thinking.
Christian philosopher and theologian Thomas Aquinas (1225–1274) had direct access to the works of Proclus, Simplicius of Cilicia, and Pseudo-Dionysius the Areopagite, and he knew about other Neoplatonists, such as Plotinus and Porphyry, through second hand sources. The German mystic Meister Eckhart (c. 1260 – c. 1328) was also influenced by neoplatonism, propagating a contemplative way of life which points to the Godhead beyond the nameable God. Neoplatonism also had a strong influence on the perennial philosophy of the Italian Renaissance thinkers Marsilio Ficino and Pico della Mirandola, and continues through 19th-century Universalism and modern-day spirituality and nondualism.
The term “Neoplatonism” refers to a philosophical school of thought that first emerged and flourished in the Greco-Roman world of late antiquity, roughly from the time of the Roman Imperial Crisis to the Arab conquest, i.e., the middle of the 3rd to the middle of the 7th century. In consequence of the demise of ancient materialist or corporealist thought such as Epicureanism and Stoicism, Neoplatonism became the dominant philosophical ideology of the period, offering a comprehensive understanding of the universe and the individual human being’s place in it. However, in contrast to labels such as “Stoic”, “Peripatetic” or “Platonic”, the designation “Neoplatonic” is of modern coinage and to some extent a misnomer. Late antique philosophers now counted among “the Neoplatonists” did not think of themselves as engaged in some sort of effort specifically to revive the spirit and the letter of Plato’s dialogues. To be sure, they did call themselves “Platonists” and held Plato’s views, which they understood as a positive system of philosophical doctrine, in higher esteem than the tenets of the pre-Socratics, Aristotle, or any other subsequent thinker. However, and more importantly, their signature project is more accurately described as a grand synthesis of an intellectual heritage that was by then exceedingly rich and profound. In effect, they absorbed, appropriated, and creatively harmonized almost the entire Hellenic tradition of philosophy, religion, and even literature—with the exceptions of Epicureanism, which they roundly rejected, and the thoroughgoing corporealism of the Stoics. The result of this effort was a grandiose and powerfully persuasive system of thought that reflected upon a millennium of intellectual culture and brought the scientific and moral theories of Plato, Aristotle, and the ethics of the Stoics into fruitful dialogue with literature, myth, and religious practice. In virtue of their inherent respect for the writings of many of their predecessors, the Neoplatonists together offered a kind of meta-discourse and reflection on the sum-total of ideas produced over centuries of sustained inquiry into the human condition.
As a natural consequence of their insistence on the undiminished relevance of the past, the Neoplatonists developed their characteristically speculative brand of philosophical enquiry in which empirical facts tended to serve as illustrations rather than heuristic starting points or test cases. Today, the Neoplatonic system may strike one as lofty, counterintuitive, and implausible, but to dismiss it out of hand is difficult, especially if one is prepared to take seriously a few fundamental assumptions that are at least not obviously wrong and may possibly be right.
The most fundamental of these assumptions, which the Neoplatonists shared with the majority of intellectuals of the ancient world, including most pre-Socratic thinkers as well as Socrates, Plato, Aristotle and their followers, is that mindful consciousness (nous, often translated as thought, intelligence, or intellect) is in an important sense ontologically prior to the physical realm typically taken for ultimate reality (Mind over Matter). There existed a dispute between Plato and Aristotle over whether or not the objects of mindful consciousness (abstract concepts, Platonic or otherwise, numbers, geometrical properties, and so forth) are also ontologically prior, but the Neoplatonists regarded this fact as a matter of inconsequential detail. And so, following a venerable and abiding tradition of Mind over Matter, Neoplatonism inevitably turned out to be an idealist type of philosophy.
The second assumption, which the Neoplatonists shared with the Stoics and the Hermetists (an influential group of Egyptian religious thinkers that predate the rise of Neoplatonism), was that reality, in all its cognitive and physical manifestations, depended on a highest principle which is unitary and singular. Neoplatonic philosophy is a strict form of principle-monism that strives to understand everything on the basis of a single cause that they considered divine, and indiscriminately referred to as “the First”, “the One”, or “the Good”. Since it is reasonable to assume, as the Neoplatonists did, that any efficient cause is ontologically prior to, and hence more real, than its effect, then, in the hierarchy of being, the first principle, whatever it is, cannot be less “real” than the phenomena it is supposed to explain. Given the veracity of the first assumption (the ontological priority of intelligence and consciousness), it follows at once that the first principle must be a principle of consciousness. In consequence, the fundamental challenge all Neoplatonists struggled to meet was essentially the following: How are we to understand and describe the emergence of the universe, with all its diverse phenomena, as the effect of a singular principle of consciousness? In particular—and in this regard Neoplatonism shares certain concerns with modern cosmology—how is it possible to understand the emergence of the physical, material universe from a singularity that is in every sense unlike this universe? Their answer to this question was entirely new, and went far beyond any prior cosmic aetiology, including that of Plato’s Timaeus, in elegance and sophistication.