The questions On the Knowledge of Christ (De scientia Christi), which develop his illumination theory of knowledge, probably came out of his inception as Master in 1254.
G. W. Leibniz, writing in the early 18th century on the future course of Sino-European relations, suggested evocatively that "the commerce of light," which is to say of illumination, or knowledge, always piggy-backs on the commerce of goods.
In his The Varieties of Religious Experience, the philosopher William James might have described it as "mystical," as in "mystical states seem to those who experience them to be also states of knowledge... illuminations, revelations, full of significance and importance, all inarticulate though they remain".
It is important to emphasize that Augustine's theory of illumination concerns all knowledge, and not specifically mystical or spiritual knowledge.
The sun metaphor of illumination — as the source of both being and of knowledge (enlightenment) — befits the universality of the hosshin perfectly.
There is some justification for this, of course, inasmuch as Christian medieval philosophers gave the theory serious and sustained discussion, and inasmuch as Augustine gave illumination a very prominent role in his theory of knowledge.
Others (Marrone 1983), treating On Truth as the earlier work, take Grosseteste now to reject an account of divine illumination in our knowledge in this life and hold his references to illumination in the context of scientific knowledge to refer to a light the human soul itself sheds on intelligible things in a process of abstraction understood along Aristotle's lines.
In particular, in his account of demonstrative science, and thus of the sort of knowledge possible for most of us in this life, is Grosseteste employing a notion of divine illumination, as he clearly does in his treatise On Truth?
Since that can be found only in the divine mind, and since we have access to the divine mind only through illumination, certain knowledge requires illumination.
