Prelude to the use of Diotima’s Eros as a form of “Philosophic” knowledge

Preliminary note: There is nothing necessarily sexual in Diotima’s Eros. If you want to know more, read Plato’s Symposium, the Song of Songs, the Definition of Literature post, or there are a great deal of other similar things that you might find profitable.

“The greatest philosopher is unable to grasp the being of a single fly.”
--St. Thomas Aquinas

To which we respond, “how is this quote true?,” a question that includes “what does it mean, how do we prove it, and what are we missing in our knowledge?

There is one obvious answer: existence is a mystery for two reasons:
A. Each individual being is linked to the whole of reality by at least God’s creative act. But God, one of the causes of the thing known is infinite and unknowable. Therefore, nothing is completely knowable.
B. Existence itself is a mystery. It cannot be given an essential definition. To one who looks long and hard enough (and I know this from sense and phenomenological experience), existence elicts a sense of wonder, even from things well-known. And wonder implies ignorance (Josef Pieper).
a. “There is an is!” –G.K. Chesterton.
b. “Why should there be being, and not nothing?” --Martin Heidegger


Essence is also a mystery, or at least an ultimately undefinable, analogous to the mystery revealed by the Fallacy of the Perfect Dictionary.

In the art of logic, the clearest knowledge of a thing includes an “Essential Definition.” One who knows a thing by essential definition knows the type of thing (genus) that it is as well as that which separates this kind of thing (species) from other species of the same type necessarily and always (specific difference). For example, the essential definition of square is “A rectangle with all sides equal.” Rectangle is the genus, all sides equal is the specific difference, square is the species.
What is missing from an essential definition? What is not grasped? When one knows a thing, the mental representation of what the thing is is in the intellect. What the thing actually is, not just the representation, is in the thing itself, and in the Mind of God, for God knows all things as maker. For true and complete knowledge, it seems that an essential definition is incomplete.
Consider an angel. Each angel is, in itself, a species. This means that the “what-it-is” is identical to the individual angel (this is different from, say, an orange, where what the orange is is different from the individual orange). If the essential definition of this angel were equivalent to having the what-it-is of the angel in the mind, than everyone who knew the essential definition would have the angel in their mind, which is absurd. Therefore, there are cases where an essential definition is not complete knowledge of an essence (the essence is the what-it-is).
With material things, one can never completely know the particular, because this would imply that the particular is in the intellect. But an intellect that knows oranges obviously does not have real oranges in it.
Even with essences of material things, the so-called “essential definition” can never be known to be complete knowledge. What an essential definition does is say “Everything with genus A and specific difference B is a C.” This statement is known to conform with what C is. The idea that every C necessarily is genus A with difference B does not imply that every C only necessarily is genus A with difference B. Because the idea in the mind that is the essential definition is not the cause of what C is (the cause of what C is is the essence of C, that to which the definition conforms), the essential definition is knowledge that provides a perfect test for C’s essence, but is not necessarily identical to C’s essence.
Hence, intellectual knowledge has been shown to be possibly insufficient. Therefore, we can justifiably investigate the knowledge gained through the Eros loved by Diotima.