Differentiation between the original and later additions of an art work has to be made as clearly and completely as possible. Generally speaking, the art historian's first consideration in regard to an old painting is its significance and importance as an historical witness. For many others, the painting, above all, is work of art, that is to say, an expression of beauty. More importance should be given to a thorough scientific examination before treatment, including the distinction between the original and later additions. Since the preservation of the original for generations to come is the most important function of the museum, priority should be given to conservation versus restoration, to physical structure versus theory of any kind.