柏拉图主义的核心是:承认抽象对象的存在(existence of abstract objects)。抽象对象并不依赖于时间和空间而存在,因此既非物理的,又非心灵的,而是存在于第三个地方。柏拉图主义的对立面是唯名論。[1] 柏拉图主义的可以应用于:性质、类型、命题、意义(英语:Meaning (philosophy of language))、数字、集合、真值等等(参见抽象对象理论)。柏拉图主义有些相关概念需要区分:哲学家承认抽象对象存在的,有时候称他们为“柏拉图主义者”;不承认的,有时候称作“唯名论者”。“柏拉图主义”和“唯名论”两个词,在哲学史中另有意义,与“抽象对象”无关,因此它们和本条目所说的当代的柏拉图主义(platonism,小写p)、当代的唯名论不同。[2]
在更窄的意义下,柏拉图主义也可以指柏拉圖實在論的学说。柏拉图主义,在这个意义下,它的核心概念(对理型论很重要)是对这两者的区分:可感知但不能认识的实在性(与赫拉克利特的变化(flux)相关,科学研究这种实在性),与不可感知却可以认识的实在性(与巴门尼德永恒的存在相关联,数学研究这种实在性)。几何学是柏拉图的主要动力,因为他受到了毕达哥拉斯的影响。理念(Forms)在柏拉图的一些对话集中得到详细阐释,如《斐多篇》《會飲篇》《理想国》等。柏拉图认为,日常世界中有对象,理念就是它们的诸原型,而日常对象则是理念的不完美复制品。批判这个理论,最著名的当属亚里士多德,其三人论证(英语:Third man argument)在古代格外出彩。
^ 1.01.1“哲学家承认抽象对象存在的,有时叫他们为柏拉图主义者;不承认抽象对象存在的,有时叫他们唯名论者。‘柏拉图主义’和‘唯名论’都有哲学史上的概念,这种语境下,和当代所说‘抽象对象’没有任何关联。注意:当代的柏拉图主义者(modern platonist。小写p以示区分),并不必然接受柏拉图的所有学说,当代的唯名论者(modern nominalists)也并不必然接受中世纪的唯名论学说。(Philosophers who affirm the existence of abstract objects are sometimes called platonists; those who deny their existence are sometimes called nominalists. The terms "platonism" and "nominalism" have established senses in the history of philosophy, where they denote positions that have little to do with the modern notion of an abstract object. In this connection, it is essential to bear in mind that modern platonists (with a small 'p') need not accept any of the doctrines of Plato, just as modern nominalists need not accept the doctrines of medieval nominalists.)” 抽象对象 (页面存档备份,存于互联网档案馆), Gideon Rosen, The Stanford Encyclopedia of Philosophy (Spring 2012 Edition), Edward N. Zalta (ed.).
^抽象对象 (页面存档备份,存于互联网档案馆), Gideon Rosen, The Stanford Encyclopedia of Philosophy (Spring 2012 Edition), Edward N. Zalta (ed.).
^O'Connell SJ, RJ, The Enneads and St Augustine's Vision of Happiness. Vigiliae Christianae 17 (1963) 129-164 (JSTOR)
^Pelikan, Jaroslav. The Christian Tradition: A History of the Development of Doctrine. Vol 1: The Emergence of the Catholic Tradition 100-600; Pelikan, Jaroslav. The Christian Tradition: A History of the Development of Doctrine. Vol 3: The Growth of Mediaeval Theology 600-1300, section, "The Augustinian Synthesis".
^The G. K. Chesterton Collection II [65 Books]. Catholic Way Publishing. 2014 [2020-03-07]. ISBN 9781783792108. (原始内容存档于2020-08-06). Plato in some sense anticipated the Catholic realism, as attacked by the heretical nominalism, by insisting on the equally fundamental fact that ideas are realities; that ideas exist just as men exist.
^[[G·K·卻斯特頓|]]. St. Thomas Aquinas. Courier Corporation. 2012 [2020-03-07]. ISBN 9780486122267. (原始内容存档于2021-02-02). The truth is that the historical Catholic Church began by being Platonist; by being rather too Platonist.
^Peter Stanford(英语:Peter Stanford). Catholicism: An Introduction: A comprehensive guide to the history, beliefs and practices of the Catholic faith. Hachette UK. 2010. ISBN 9781444131031. Both Aristotle and Plato were crucial in shaping Catholic thinking
^Between Past and Future. Penguin. 2006 [2020-03-07]. ISBN 9781101662656. (原始内容存档于2020-08-06). To the extent that the Catholic Church incorporated Greek philosophy into the structure of its doctrines and dogmatic beliefs