This-ness, Is-ness, and Being

So, in my Victorian literature class we've been discussing the poet and priest Gerard Manley Hopkins (who, by the way is amazing...okay, I'm totally interrupting myself, but what's not to love in poetry like this:
"As kingfishers catch fire, dragonflies draw flame;
As tumbled over rim in roundy wells
Stones ring; like each tucked string tells, each hung bell's
Bow swung finds tongue to fling out broad its name;
Each mortal thing does one thing and the same:
Deals out that being indoors each one dwells;
Selves--goes itself; myself it speaks and spells,
Crying What I do is me: for that I came."
Okay, end of digression...)
Anyway, Hopkins coined the word "inscape" to refer to a thing's (or person's or landscape's) this-ness, its individual essential quality (he borrowed the idea from Duns Scotus' haecceitas, to give credit where it's due). Bascially, everything has this completely unique "self" (which is why Hopkins hated seeing nature destroyed: each tree and hill and scene's inimitable inscape is lost to us forever).
I like this idea, and have been rolling it around in my head this term, and yesterday I came across this passage in Madeleine L'Engle's book A Circle of Quiet:
"Sartre felt depressed and threatened by [the isness of an oak tree]; the idea that the oak tree simply is seems to diminish him. I suppose the perfect isness of anything would be frightening without the hope of God. An oak tree is, and it doesn't matter to it--at least Sartre thinks it doesn't; it is not a thinking oak. Man is; it matters to him; this is terrifying unless it matters to God, too, because this is the only possible reason we can matter to ourselves..." (8).
Some of L'Engle's theology is a bit wacky at times, but somehow Hopkins and this passage are sort of bouncing around in my head right now and I thought I'd get them out there.
For what it's worth.
P.S. Hopkins is even better read aloud...