 Edmund Husserl introduced two sorts of innovation to the study of categories. First, while Aristotle used language as a clue to ontological categories, and Kant treated concepts as the route to categories of objects of possible cognition, Husserl explicitly distinguished categories of meanings from categories of objects, and attempted to draw out the law-like correlations between categories of each sort (Smith 2007, 139ff.). Secondly, whereas Aristotle and Kant each lay out a single system of categories, Husserl distinguishes two ways of arriving at top-level ontological classifications: by formalization and by generalization, yielding two separate, orthogonal, systems of categories, in two different dimensions (cf. Smith 2004, chapter 8).