Sin has many tools, but a lie is the handle which fits them all.

Holmes’s aphorism treats lying not as one vice among others but as the enabling mechanism that makes other wrongdoing workable. “Sin” may take many forms—greed, cruelty, betrayal—but deception is the universal grip that lets those acts be planned, justified, concealed, or repeated. The metaphor of a “handle” suggests leverage and usability: a lie gives moral failure traction in the world by smoothing over consequences and quieting conscience. The line also implies that truth-telling is a kind of master-virtue; by refusing the lie, one removes the common instrument that empowers many other harms.