Nothing is better known than the distinction of social ranks which exists in every community, and nothing is harder to define.
 Oliver Wendell Holmes Sr., The Professor at the Breakfast-Table (1860). copy citation

Context

“I go politically for equality,—I said,—and socially for the quality. Who are the “quality,”—said the Model, etc., in a community like ours? I confess I find this question a little difficult to answer,—I said. —Nothing is better known than the distinction of social ranks which exists in every community, and nothing is harder to define. The great gentlemen and ladies of a place are its real lords and masters and mistresses; they are the quality, whether in a monarchy or a republic; mayors and governors and generals and senators and ex-presidents are nothing to them.” source