Parum proficit scire quid fieri debet

Parum proficit scire quid fieri debet, si non cognoscas quomodo sit facturum. It avails little to know what ought to be done, if you do not know how it is to be done. 2 Co. Inst. 503.

A Law Dictionary, Adapted to the Constitution and Laws of the United States. By John Bouvier. Published 1856.