“The great object of composition being always to secure unity; that is, to make out of many things one whole; the first mode in which this can be effected is, by determining that one feature shall be more important than all the rest, and that the others shall group with it in subordinate positions. Thus, also, good pictures have always one light larger and brighter than the other lights, or one figure more prominent than the other figures, or one mass of colour dominant over all the other masses; and in general you will find it much benefit your sketch if you manage that there shall be one light on the cottage wall, or one blue cloud in the sky, which may attract the eye as leading light, or leading gloom, above all others. But the observance of the rule is often so cunningly concealed by the great composers, that its force is hardly at first traceable; and you will generally find they are vulgar pictures in which the law is strikingly manifest.”

– John Ruskin