…the Church is generally seen in the light of the last heresy. The Church is supposed to consist chiefly of the things of which that heresy happens to disapprove. So much of the Protestant tradition still remains that a great many people suppose that the chief marks of Catholicity are those which stood out as stains in the eyes of the last school of critics. Romanism is supposed to be made up of Popery and Purgatory and the Confessional, with the queerest things thrown in, such as incense and rosaries and the images of saints. But these were often the things most important to [these opponents of Catholicism], not most important to Catholics; and not most important to the other opponents of Catholics.
-The Well and the Shallows (1935)
Or, more briefly, as Chesterton puts it in The Common Man (1950)
The Catholic Church is always being defined in terms of the particular quarrel that she happens to have with particular people in a particular place.