“And all the families of the families of that one mouse! With a stamp of your foot, you annihilate first one, then a dozen, then a thousand, a million, a billion possible mice!”

"So they're dead," said Eckels. "So what?"

This quote demonstrates Eckels’s careless and selfish attitude, long before personal terror affects his behavior. When Travis explains that killing one mouse in the past can lead to the death of a billion mice in the future, Eckels displays indifference. He refuses to understand the significance of the lives of the mice without additional explanation. After all, he is a wealthy hunter who does not care about the lives of animals, and he cannot foresee the possibility that one tiny life might be connected to others in a meaningful way. His question, “So what?” is phrased as if it were a rebuttal to Travis’s point, discounting the rule Travis intends to establish and defend.

Even after Travis responds to the question and Eckels agrees to the explanation, Eckels’s careless and indifferent attitude persists. He never thinks about the safety of his fellow travelers, abandons them in a fit of fear, and, when things go unspeakably awry, he whips out his checkbook as if he might solve every issue by paying Travis off. Eckels’s concerns end with himself.

People called us up, you know, joking but not joking. Said if Deutscher became President they wanted to go live in 1492. Of course it’s not our business to conduct Escapes, but to form Safaris. Anyway, Keith’s President now. All you got to worry about is—.”

"Shooting my dinosaur," Eckels finished it for him. 

Immediately following his reflections about how wonderful the time machine is, Eckels holds a discussion of the election results with the man behind the desk. Eckels states that if the election had had an unfavorable result, he might have wanted to escape the outcome by running away to the past. The man has quickly explained that escaping through time isn’t permitted, redirecting Eckels’s thinking.

Eckels’s impatience and excitement about the coming adventure immediately surface. He abandons the political discussion, whose subject foreshadows concluding events, and he longs to get on with killing a dinosaur. Tellingly, he uses the pronoun “my” as he refers to the animal. Later, it will become clear that no one person either kills or owns it; it takes a group to bring the animal down, and they must leave its body in the past.

Eckels—perhaps because he paid an enormous sum of money for the opportunity to hunt—already displays the self-centered attitude that will land him, the hunting party, and the entire world in trouble. His focus on personal gratification, rather than on responsible and serious matters, indicates qualities of character that will lead to nowhere good.