A man's opinions, look you, are generally of much more value than his arguments.
 Oliver Wendell Holmes Sr., The Professor at the Breakfast-Table (1860). copy citation

Context

“I shall not often give arguments, but frequently opinions,—I trust with courtesy and propriety, but, at any rate, with such natural forms of expression as it has pleased the Almighty to bestow upon me. A man's opinions, look you, are generally of much more value than his arguments. These last are made by his brain, and perhaps he does not believe the proposition they tend to prove,—as is often the case with paid lawyers; but opinions are formed by our whole nature,—brain, heart, instinct, brute life, everything all our experience has shaped for us by contact with the whole circle of our being.” source