Final answer:
The quoted passage does not directly match any of the choices provided (Fahrenheit 451, 1984, Brave New World, The Fountainhead). However, it reflects philosophical ideas similar to themes found in these dystopian novels, and may allude to concepts like those in Plato's allegory.
Step-by-step explanation:
The quote “It isn't a circle—it is simply a long line—as in geometry, you know, one that reaches into infinity. And because we cannot see the end—we also see the changes—who dream, who will not give up—are called those who see only the circle we call them the 'realist'!” does not appear to match verbatim to any of the provided options, which include Fahrenheit 451, 1984, Brave New World, or The Fountainhead. However, concepts in the quote relating to infinity and perspectives on reality reflect philosophical discussions similar to those found in the dystopian themes of the listed books. The quote could potentially be a paraphrased or thematic expression aligning with Plato's allegory of the cave described in 'The Republic', where the reality perceived by prisoners is but shadows of the true form. However, given how none of the literary works listed overtly discuss the geometry concepts mentioned in the quote, the quote may come from a different source not listed in the options. As such, without further context or information, it is not possible to definitively pinpoint which literary work the quote is from.