There's a mighty big difference between good, sound reasons and reasons that sound good.

Hillis’s aphorism draws a sharp line between arguments that are genuinely well-founded (“good, sound reasons”) and arguments that merely have the surface features of plausibility (“reasons that sound good”). The wordplay highlights how rhetoric, confidence, and familiar talking points can mimic rationality, persuading audiences without providing solid evidence or logic. The quote is a compact warning about cognitive bias and social persuasion: we often accept explanations because they are fluent, emotionally satisfying, or align with what we already believe. Its significance lies in urging critical scrutiny—testing claims for validity, evidence, and coherence rather than for polish or appeal.