Against these forces Asimov placed the scientists, who may be passionate enough in pursuit of their goals (Aton blusters at Theremon, and another astronomer, Beenay, attacks Latimer), but they are willing to accept whatever "truth" best explains the facts. In earlier stories ("Black Friar of the Flame," which was written early in 1939, "Half-Breed," ''The Secret Sense," etc.), Asimov had sometimes allowed emotion to become a motivating force. In "Nightfall" he established the position that he was to maintain throughout most of the rest of his work: rationality must struggle to prevail in a world made difficult not only by the mysteries and hard truths of the universe but by people unable or unwilling to think clearly. The subject of "Nightfall" is ignorance; ignorance of the laws that govern the universe, ignorance of phenomena such as "night" and "stars," which makes the Lagashians, even the scientists, victims of their fears.