Heaven and hell suppose two distinct species of men, the good and the bad. But the greatest part of mankind float betwixt vice and virtue.

Hume challenges the stark moral dualism implied by traditional religious imagery of heaven and hell. Instead of dividing humanity into two clear “species” (the saved and the damned), he emphasizes moral gradation: most people are mixed characters whose conduct shifts with circumstance, habit, and temptation. The remark aligns with Hume’s broader skepticism about metaphysical and theological certainties and his empiricist attention to ordinary human psychology. It also reflects his moral philosophy, which treats virtue and vice as matters of sentiment, character, and social evaluation rather than absolute categories. The quote’s force lies in its insistence on moral complexity and the inadequacy of rigid, binary judgments.