I shall have a good deal to say about right reasoning; and in default of better I had reckoned that as a Topic of Vital Importance. But I do not know that the theory of reasoning is quite vitally important. That it is absolutely essential in metaphysics, I am as sure as I am of any truth of philosophy. But in the conduct of life, we have to distinguish everyday affairs and great crises. In the great decisions, I do not believe it is safe to trust to individual reason. In everyday business, reasoning is tolerably successful; but I am inclined to think that it is done as well without the aid of theory as with it. A Logica Utens, like the analytical mechanics resident in the billiard player’s nerves, best fulfills familiar uses.
http://www.commens.org/dictionary/entry/quote-cambridge-lectures-reasoning-and-logic-things-philosophy-and-conduct-life