[1] This can apply to properties, types, propositions, meanings, numbers, sets, truth values, and so on (see abstract object theory).
The central concept of Platonism, a distinction essential to the Theory of Forms, is the distinction between the reality which is perceptible but unintelligible, associated with the flux of Heraclitus and studied by the likes of science, and the reality which is imperceptible but intelligible, associated with the unchanging being of Parmenides and studied by the likes of mathematics.
The Forms are typically described in dialogues such as the Phaedo, Symposium and Republic as perfect archetypes of which objects in the everyday world are imperfect copies.
The only true being is founded upon the forms, the eternal, unchangeable, perfect types, of which particular objects of moral and responsible sense are imperfect copies.
[6] The following excerpt may be representative of Plato's middle period metaphysics and epistemology: [Socrates:] "Since the beautiful is opposite of the ugly, they are two."
[6] And, since in this cognition, the three parts of the soul, which are reason, spirit, and appetite, all have their share, we get the three virtues, Wisdom, Courage, and Moderation.
[12]The Phaedo most famously caused problems to scholars who were trying to make sense of this aspect of Plato's theory of the soul, such as Broadie[13] and Dorothea Frede.
Plato delivered his lectures at the Platonic Academy, a precinct containing a sacred grove outside the walls of Athens.
It was still largely skeptical, denying the possibility of knowing an absolute truth; both Arcesilaus and Carneades argued that they were maintaining a genuine tenet of Plato.
The eclectic nature of Platonism during this time is shown by its incorporation into Pythagoreanism (Numenius of Apamea) and into Jewish philosophy[15] (Philo of Alexandria).
In the third century, Plotinus recast Plato's system, establishing Neoplatonism, in which Middle Platonism was fused with mysticism.
Soul, being chained to matter, longs to escape from the bondage of the body and return to its original source.
[16] Plotinus' disciple, Porphyry, followed by Iamblichus, developed the system in conscious opposition to Christianity—even as many influential early Christian writers took inspiration from it in their conceptions of monotheistic theology.
The Platonic Academy was re-established during this period; its most renowned head was Proclus (died 485), a celebrated commentator on Plato's writings.
[17] St. Augustine was heavily influenced by Platonism as well, which he encountered through the Latin translations of Marius Victorinus of the works of Porphyry and/or Plotinus.
[19] Christoplatonism is a term used to refer to a dualism opined by Plato, which holds spirit is good but matter is evil,[20] which influenced some Christian churches, though the Bible's teaching directly contradicts this philosophy and thus it receives constant criticism from many teachers in the Christian Church today.
According to the Methodist Church, Christoplatonism directly "contradicts the Biblical record of God calling everything He created good.
"[20] Apart from historical Platonism originating from thinkers such as Plato and Plotinus, we also encounter the theory of abstract objects in the modern sense.
Plato's works have been decisively influential for 20th century philosophers such as Alfred North Whitehead and his Process Philosophy; and for the critical realism and metaphysics of Nicolai Hartmann.
In contemporary philosophy, most Platonists trace their ideas to Gottlob Frege's influential paper "Thought", which argues for Platonism with respect to propositions, and his influential book, The Foundations of Arithmetic, which argues for Platonism with respect to numbers and is a seminal text of the logicist project.
[21] Contemporary analytic philosophers who espoused Platonism in metaphysics include Bertrand Russell,[21] Alonzo Church,[21] Kurt Gödel,[21] W. V. O. Quine,[21] David Kaplan,[21] Saul Kripke,[21] Edward Zalta[22] and Peter van Inwagen.
In contemporary Continental philosophy, Edmund Husserl's arguments against psychologism are believed to derive from a Platonist conception of logic, influenced by Frege and his mentor Bolzano.
Other prominent contemporary Continental philosophers interested in Platonism in a general sense include Leo Strauss,[25] Simone Weil,[26] and Alain Badiou.
Julius Evola incorporated Platonic metaphysics into his vision of Roman pagan revival, aligning with his Traditionalist critique of modernity.
Arturo Reghini, an Italian esotericist and collaborator of Evola, also promoted Neoplatonic ideas in his efforts to revive ancient Roman religion.