Criticism is concerned with evaluation. There may be evaluative principles implicit in this or that form of theory, but theory in and of itself is not prescriptive.
Paul FryI make a distinction between theory and methodology, the latter being the practical deployment of a premise. Theory on the contrary may well be applied, hence becomes methodology without a hitch, but isn't necessarily practical at all.
Paul FryBoth the 18th and the early 20th centuries, however, feature brilliant attacks on originality, and it's no doubt one of the hallmarks of romanticism to care about originality and suppose with a sometimes naive spontaneity that it's all that matters.
Paul Fry