No men can have satisfactory relations with each other until they have agreed on certain ultimata of belief not to be disturbed in ordinary conversation, and unless they have sense enough to trace the secondary questions depending upon these ultimate beliefs to their source.
 Oliver Wendell Holmes Sr., The Autocrat of the Breakfast-Table (1858). copy citation

Context

“I don’t doubt it, but I will tell you what I have found spoil more good talks than anything else;—long arguments on special points between people who differ on the fundamental principles upon which these points depend. No men can have satisfactory relations with each other until they have agreed on certain ultimata of belief not to be disturbed in ordinary conversation, and unless they have sense enough to trace the secondary questions depending upon these ultimate beliefs to their source. In short, just as a written constitution is essential to the best social order, so a code of finalities is a necessary condition of profitable talk between two persons. Talking is like playing on the harp;” source