Ill habits gather by unseen degrees - As brooks make rivers, rivers run to seas.

Dryden’s couplet warns that vice and moral decline rarely arrive all at once; they accumulate gradually, almost imperceptibly, through repeated small choices. The natural imagery—brooks becoming rivers and rivers flowing to the sea—casts habit as a force of accretion: tiny beginnings can grow into powerful currents that are difficult to resist or reverse. The lines also imply a kind of inevitability once a pattern is established, urging vigilance at the earliest stages of conduct. In a broader ethical sense, the couplet reflects a classical and Christian moral psychology common in Dryden’s age: character is formed by repeated actions, and what seems trivial today can shape one’s destiny over time.