We do not wholly possess an experience until, having merged ourselves in it, we then react upon it and become conscious of its significance. A novel, a play, a picture interests us, and we surrender to the enjoyment of the moment. Afterwards we think about our pleasure, defining the nature of the experience and analyzing the means by which it was produced, the subject of the work and the artist's method of treating it. It may be that we tell our pleasure to a friend, glad also perhaps to hear his opinion of the matter. The impulse is natural; the practice is helpful. And herein lies the origin of criticism. In so far as an appreciator does not rest in his immediate enjoyment of a work of art, but seeks to account for his pleasure, to trace the sources of it, to establish the reasons for it, and to define its quality, so far he becomes a critic. As every man who perceives beauty in nature and takes it up into his own life is potentially an artist, so every man is a critic in the measure that he reasons about his enjoyment. The critical processes, therefore, are an essential part of our total experience of art, and criticism may be an aid to appreciation. The function of criticism has been variously understood through the centuries of its practice. Early modern criticism, harking back to the method of Aristotle, concerned itself with the form of a work of art. From the usage of classic writers it deduced certain "rules" of composition; these formulas were applied to the work under examination, and that was adjudged good or bad in the degree that it conformed or failed to conform to the established rules. It was a criticism of law-giving and of judgment. In the eighteenth century criticism extended its scope by the admission of a new consideration, passing beyond the mere form of the work and reckoning with its power to give pleasure. Addison, in his critique of "Paradise Lost," still applies the formal tests of the Aristotelian canons, but he discovers further that a work of art exists not only for the sake of its form, but also for the expression of beautiful ideas. This power of "affecting the imagination" he declares is the "very life and highest perfection" of poetry. This is a long step in the right direction. With the nineteenth century, criticism conceives its aims and procedure in new and larger ways. A work of art is now seen to be an evolution; and criticism adapts to its own uses the principles of historical study and the methods of scientific investigation. Recognizing that art is organic, that an art-form, as religious painting or Gothic architecture or the novel, is born, develops, comes to maturity, lapses, and dies, that an individual work is the product of "race, environment, and the moment," that it is the expression also of the personality of the artist himself, criticism no longer regards the single work as an isolated phenomenon, but tries to see it in its relation to its total background.