Poetry Day - No Beauty We Could Desire
Here is a poem by CS Lewis himself, that presents something of his 'Argument from Desire', capturing that fleeting, unnameable and ungraspable Sehnsucht in the first two verses.

No Beauty We Could Desire
Yes, you are always everywhere. But I,
Hunting in such immeasurable forests,
Could never bring the noble Hart to bay.
The scent was too perplexing for my hounds;
Nowhere sometimes, then again everywhere.
Other scents, too, seemed to them almost the same.
Therefore I turn my back on the unapproachable
Stars and horizons and all musical sounds,
Poetry itself, and the winding stair of thought.
Leaving the forests where you are pursued in vain
—Often a mere white gleam—I turn instead
To the appointed place where you pursue.
Not in nature, not even in Man, but in one
Particular Man, with a date, so tall, weighing
So much, talking Aramaic, having learned a trade;
Not in all food, not in all bread and wine
(Not, I mean, as my littleness requires)
But this wine, this bread … no beauty we could desire.
C. S. Lewis
(Note: I don't think Lewis means that Sehnsucht goes away when you find Christ - something still comes over me when I smell a bonfire or read a certain poem - I think it is more that you then know from where it comes and what it means.)
Picture from http://www.topnews.in/files/saving-forests.JPG