True it is that in many or most cases we have got so used to this ornament, that we look upon it as if it had grown of itself, and note it no more than the mosses on the dry sticks with which we light our fires. So much the worse! for there IS the decoration, or some pretence of it, and it has, or ought to have, a use and a meaning. For, and this is at the root of the whole matter, everything made by man's hands has a form, which must be either beautiful or ugly; beautiful if it is in accord with Nature, and helps her; ugly if it is discordant with Nature, and thwarts her; it cannot be indifferent: we, for our parts, are busy or sluggish, eager or unhappy, and our eyes are apt to get dulled to this eventfulness of form in those things which we are always looking at. Now it is one of the chief uses of decoration, the chief part of its alliance with nature, that it has to sharpen our dulled senses in this matter: for this end are those wonders of intricate patterns interwoven, those strange forms invented, which men have so long delighted in: forms and intricacies that do not necessarily imitate nature, but in which the hand of the craftsman is guided to work in the way that she does, till the web, the cup, or the knife, look as natural, nay as lovely, as the green field, the river bank, or the mountain flint.
To give people pleasure in the things they must perforce USE, that is one great office of decoration; to give people pleasure in the things they must perforce MAKE, that is the other use of it.
From William Morris, "The Lesser Arts," in Hopes and Fears for Art
UPDATE: I was reminded by this of this old post. Wow; that was over a year ago....