“Logic is the most useful tool of all the arts. Without it no science can be fully known.”
Summa Logicae (c. 1323), Prefatory Letter, as translated by Paul Vincent Spade (1995) http://www.pvspade.com/Logic/docs/ockham.pdf
Context: Logic is the most useful tool of all the arts. Without it no science can be fully known. It is not worn out by repeated use, after the manner of material tools, but rather admits of continual growth through the diligent exercise of any other science. For just as a mechanic who lacks a complete knowledge of his tool gains a fuller [knowledge] by using it, so one who is educated in the firm principles of logic, while he painstakingly devotes his labor to the other sciences, acquires at the same time a greater skill at this art.
