Common sense and a sense of humor are the same thing, moving at different speeds. A sense of humor is just common sense, dancing.

Clive James links two faculties often treated as opposites: sober practicality (“common sense”) and playful wit (“a sense of humor”). By calling them “the same thing, moving at different speeds,” he suggests humor is not irrationality but accelerated perception—an ability to see the obvious connections, contradictions, and social truths quickly enough to make them amusing. The image of common sense “dancing” implies that comedy is disciplined intelligence given rhythm and lightness: it keeps contact with reality while delighting in its incongruities. The remark also deflates pretension about humor as mere frivolity; for James, good jokes are a form of clear thinking, delivered with agility and charm.