Wallace Stevens really dug certain words. He liked "purple" and "parasol," but nothing compares to the way that he loved the word "behold." Stevens drops the word twice in the poem and gives the word some special weight, and it pops up in a ton of his other stuff, too.
You would be more likely to find "behold" in the Bible than in a twentieth-century, Modernist poem, and Stevens is using this to his advantage. "Behold" suggests the witnessing of miracles, amazing things, awesome scenes. You might behold God's creations and revelations, but you certainly don't behold the bologna and cheese sandwich you made for lunch. But hey, that all depends on your perspective (or so Stevens might say).