 Roman Ingarden (1960 [1964], 22ff) took Husserl’s multi-dimensional ontology one step further. Like Husserl, he distinguished formal categories from material categories, but he also distinguished categories in a third dimension: existential categories (those describing an entity’s mode of being). The highest existential categories on Ingarden’s list are the real (spatio-temporal being), the ideal (abstract), the absolute (completely independent, atemporal), and purely intentional (consciousness-dependent). While any conceivable entity should be uniquely locatable in a single category of each dimension, the three sorts of ontology are mutually orthogonal, providing different most abstract ways of considering the putative entity in question. Thus, e.g., a sculpture might be categorized formally as an object, materially as a work of art, and existentially as purely intentional.