Besides the general mental faculty, more or less developed in different individuals, of sentiment and artistic feeling, there exists more or less developed in different circles of society and especially in families, a special capacity which I call understanding. The gist of this capacity is a conventional sense of proportion, and a conventional and particular outlook on things. Two people of the same set or family who have this faculty, always permit an expression of feeling up to a certain point beyond which they both see only empty phrases. They both see where praise ceases and irony begins, where enthusiasm ends and pretence begins—which may all seem quite different to people having different ideas. People of the same understanding are struck by anything equally, chiefly on its comic, its beautiful, or its nasty side. To help this common understanding between people of the same set or family, a language of their own establishes itself—their own special turns of speech and even words, which indicate shades of meaning non-existent for others. In our family, this understanding was developed in the highest degree between papa and us brothers. Dubkóv, too, fitted well in with our circle and understood. Dmítri, however, though far more intelligent, was dull in this respect.
—Tolstoy (Youth, pp. 332f., trans. the Maudes)