The Great Conversation:
By Gabriel Blanchard
This series is about the great ideas; so what are ideas?
At its core, an idea is a fairly simple thing: it’s a thought; any thought. A book, a sentence, a single word can express an idea. Language is inseparable from ideas.
This straightforward beginning becomes increasingly elaborate as far back as the pre-Socratic Greek philosophers of the seventh and sixth centuries BC. Heraclitus, a native of Ephesus on the eastern shore of the Ægean Sea, took up the ordinary word λόγος (logos), which meant “word” but also “discourse, argument, reason,” and a few other things besides; it is distantly related to the Latin word lēx, “law.” Heraclitus used the term to indicate a unifying structure or underlying principle of reality as a whole, sustaining its endless fluctuations and changes. Partly similar concepts can be found running through the Chinese doctrine of the Dao, or the Buddhist understanding of dharma. The concept became increasingly important in Hellenistic philosophy: the Jewish scholar Philo called the wisdom by which God made the world logos, and the Stoics used the same word to describe the divine principle that they believed animated the universe; by the close of the first century, the Gospel of John—generally believed to have been composed in Ephesus—was identifying Jesus of Nazareth as the personal incarnation of the universal logos.
The notion that the world is somehow animated by, or subsists on, ideas, is thus a very ancient and widespread one. In the generation before Plato, Pythagoras adopted an especially strange doctrine about ideas, asserting that “all is number.” What exactly was meant by this cryptic statement is a little difficult, but the Pythagoreans certainly studied mathematical relationships (such as the proportion between the length of a lyre string and the note it gave when plucked), assigned mystical significance to numbers, and even succeeded—to their horror—in proving the existence of irrational numbers. The changeless properties of number, set against the unceasing flux that Heraclitus proposed, may have been what inspired Plato to set forth the theory of the Forms. This theory went further than either Heraclitus or Pythagoras had done; everything in the material world was reduced to a kind of shadowy half-existence, reflecting one of the Forms, ideas which were the true realities and dwelt in their own exalted realm.
His most celebrated pupil, Aristotle, disputed the doctrine of the Forms (which Plato himself had considered certain critiques of, notably in the Parmenides). While accepting the idea that essences, or substances, were a kind of idea, he did not endorse the notion that the Forms had a separate existence in their own dimension: rather, Aristotle said, the form of a thing was united with its matter, imbuing it not with a mere reflection of reality but with a real nature of its own. The contrast between Platonic “transcendental” thought and Aristotelian “terrestrial” thought has remained a perennial motif in Western philosophy since, and is illustrated in the page image of this post (Raphael’s The School of Athens), which shows Plato pointing heavenwards and Aristotle gesturing to the earth.
The problem of “where” ideas are metaphysically “located” naturally relates to the problem of how we know them, so that ideas form a natural bridge between ontology (the study of being) and epistemology (the study of knowledge). There was a good deal of diversity in classical antiquity about how we know things, and indeed about whether we can know things; though Plato is famous for advancing the notion that all genuine knowledge is recollection, the Academy after his death became a major center of skepticism, casting doubt on all claims of knowledge. With the neo-Platonist movement, however, of which Plotinus and St. Augustine were the most important founders, the concept of knowledge as a divine gift of illumination in the human mind became standard for many centuries.
This began to change with the dawn of Scholasticism. Beginning in the late eleventh and early twelfth centuries, a great revival of learning took place, thanks in part to a new access to Islamic commentaries on the writings of Aristotle, obtained through the Crusades and the Reconquista. A new wave of rationalism became popular in the universities of France, Italy, and England (St. Thomas Aquinas being its most famous exponent today). An Aristotelian epistemology, based on reasoned abstraction from sense data.
This reopened many debates, including a version of the controversy about the Forms. For the Medievals, the question was about universals: is it possible to speak of the Form of rose-ness as a real, independent reality, or is it only a conventional name for a group of things that have similar properties but no inherent, metaphysical nature that unites them? The quarrel between the realists, who affirmed the existence of universals, and the nominalists, who considered them mere names, went on from the career of Peter Abelard in the early twelfth century until the Black Death in the mid-fourteenth, which ravaged the great universities as much as anywhere else.
Plato, The Republic, Book VII
Aristotle, Metaphysics, Book VII
The Epistle to the Hebrews
Sextus Empiricus, Against the Learned
St. Thomas Aquinas, Summa Theologiæ II.1 Q109, A1
William of Ockham, Sum of Logic