Q. For more than two decades I have taught and insisted that editors view “on the one hand” as joining with “on the other hand.” Both should be present and what follows each should be parallel. CMOS does not acknowledge that need. In fact, the book constantly uses “on the other hand” without “on the one hand.” How can you have an “other” without the “one”?
A. You can have it because parts of a sentence may be implied. We write, for instance, “Kate took the car; Norm, the subway,” understanding “took.” Liberties like this give English a pleasing fluidity; completely mechanical writing is usually bad writing.