All medial objects, like works of art, are generally purely intentional objects. Nevertheless, different classes of such objects – film versus painting, literature versus radio – have ontological peculiarities that must be tracked. These peculiarities can be portrayed as variable forms of mediation. Mediation of reality is already effected through the eye and ear, which becomes a prototype of mediation in general. A first thought of mediation in terms of what Arnheim called Materialtheorie, a way of acknowledging how a material alters similar contents (a prefiguring of his idea of the "representational concept"). The best way to track medial difference is through "determinacy" (Ingarden) or "accident" (Arnheim). This refers technically to the number of real world determinacies that have been projected into the work. Classes of technologies considered today as "reproductive arts' are interesting because they routinely package and reproduce sets of determinacies. Determinacies are schematic guidelines for how media in general and individual medial works, in particular, may be interpreted.