. . . or the Thing-in-Itself.
Kant used the term in his Critique of Pure Reason and it's stuck in my head ever since that freshman survey of philosophy class with Dr. Gould back in 1960.
If I understood the meaning of the term then, however briefly, I've surely forgotten it now.
But those words are what spring to mind when I see a close up picture that focuses on the essential 'thingness' of things, be they eggplants or pepper seeds . . .
. . . or a fallen poplar leaf.
Then, of course, thinking of Kant leads me to Monty Python and the Philosophers' Song.
And it's downhill from there.