I think the answer to my riddle is emergence. Emergence is to essence as inspiration is to existence . . . as poetry is to philosophy.
In testing the analogy, I've been toying with a related matter. Is there a supplement for "accident"? In philosophy, we like to distinguish between the essential and "accidental" properties of things. At one point, I had the intuition that "accidence" is on the power (i.e., poetry) side of the pangrammatical divide. But I kept it on the knowledge (philosophy) side because accidents strike me as properties of things and facts, not people and acts. What then is to emergence, as accidence is to essence?
The answer, I think is transience. People are transient as things are accidental. These are important moments it the relationship between becoming and emergence, being and essence.
P.S. Surfaces are to emergence as appearances are to essence.