We went to the book, not the quote sites. The Internet Archive holds a scan whose full text carries the sentence in Chapter III, “The Great Stream,” in the two-sentence paragraph beginning “Struggle as we may.” Archive.org’s catalogue entry files that scan as “Pantheon Books, 1951,” but the artifact itself says otherwise: the title page reads “Vintage Books, a Division of Random House,” and the cover carries the number V 468 and an ISBN — and ISBNs did not exist in 1951. It is a Vintage paperback reprinting the 1951 Pantheon text, and its copyright page still carries the original notice, “Copyright, 1951, by Pantheon Books.”
That limits what we can honestly claim. A modern Vintage edition reproduces the paragraph identically — but two Vintage printings agreeing rules out nothing about the 1951 hardcover, and Vintage’s own front matter says the book was “originally published in slightly different form” in hardcover by Pantheon in 1951, the paperback following in 1968. That gap is real and we have not closed it: we have not inspected the Pantheon hardcover, so we cite the chapter and the Vintage text rather than claim first-edition wording we have not seen. Open Library’s catalogue record independently fixes first publication at Pantheon Books, New York, 1951, 152 pages — the date that settles the rights question.
One more thing we could not confirm: an exact page number. The scan is imaged as two-page spreads, and the passage sits on the spread footed “42 / 43” without resolving to a single page. We cite the chapter rather than guess the page — and we note that no quote site we found cites a chapter at all.