While I invite this discussion of Timaeus — and Plato’s unwritten doctrine — to go where it wants to go, I’d like start by looking into this beautiful and suggestive passage.
In our former discussion I distinguished two kinds of being—the unchanging or invisible, and the visible or changing. But now a third kind is required, which I shall call the receptacle or nurse of generation. There is a difficulty in arriving at an exact notion of this third kind, because the four elements themselves are of inexact natures and easily pass into one another, and are too transient to be detained by any one name; wherefore we are compelled to speak of water or fire, not as substances, but as qualities. They may be compared to images made of gold, which are continually assuming new forms. Somebody asks what they are; if you do not know, the safest answer is to reply that they are gold. In like manner there is a universal nature out of which all things are made, and which is like none of them; but they enter into and pass out of her, and are made after patterns of the true in a wonderful and inexplicable manner. The containing principle may be likened to a mother, the source or spring to a father, the intermediate nature to a child; and we may also remark that the matter which receives every variety of form must be formless, like the inodorous liquids which are prepared to receive scents, or the smooth and soft materials on which figures are impressed. In the same way space or matter is neither earth nor fire nor air nor water, but an invisible and formless being which receives all things, and in an incomprehensible manner partakes of the intelligible.
https://www.gutenberg.org/files/1572/1572-h/1572-h.htm
As may be painfully obvious by now, I am “obsessed” with the relationship between “quality” and “form.” Here, to me anyway, the “father” plays the role of “form” and the mother the role of “quality.” I insist on “quality” because these days “matter” is strongly associated not with quality but with mathematical form. The matter of physics is not intended here.
Indeed,
the matter which receives every variety of form must be formless
Mother, matter, matrix. “Formless.” I take this to be a synonym of “ineffable.” We can only say “too much.” And yet philosophy is “a thrust against the limits of language.”
I interpret this, bringing my own present concerns to the text as anyone must, in terms of objects in the world as the “child” of the mother and father, of the dyad and the one, of nonbeing and being. So this passage, for me, connects to the unwritten doctrine.
How does “matter” (quality) “partake of the intelligible” ? I don’t present this as an empirical question. Rather, what is a good explication or unfolding of this vague expression ?
How should we understand “quality” or “matter” here ? My leaning is toward the “quality” of “the object as perceived.” The redness and shape and smell and emotional “impact” of the present rose.
How should we understand “form” ? My leaning is toward “the categorical.” The rose is a rose. But even the unity of the singular rose is a unity of “aspects.” We see the same rose, through different pairs of eyes, at different times. We can “intend” ( discuss, remember ) that particular rose in its perceptual absence.
But what do others make of this passage ?
Here’s Wiki’s sketch of “the unwritten doctrine” that I find relevant to the passage above:
The One and the Indefinite Dyad are the ultimate ground of everything because the realm of Plato’s Forms and the totality of reality derive from their interaction. The whole manifold of sensory phenomena rests in the end on only two factors. Form issues from the One, which is the productive factor; the formless Indefinite Dyad serves as the substrate for the activity of the One. Without such a substrate, the One could produce nothing. All Being rests upon the action of the One upon the Indefinite Dyad. This action sets limits to the formless, gives it Form and particularity, and is therefore also the principle of individuation that brings separate entities into existence. A mixture of both principles underlies all Being.
I suggest that chora is the dyad.