 Sturm’s argument against the third option of the trilemma runs as follows. If one defines (as scholastics usually do) a substantial form in terms of the role that the form plays in explaining and accounting for the nature of composite beings, then what is called a ‘substantial form’ cannot belong to the ontological category of a substance, but only to the category of ‘relatives’ or relational things. Sturm stresses that “the entire nature of a form generally and essentially consists of a relation” (PE I: 94). Forms are not beings in themselves, but ways in which certain beings operate and undergo changes. Against the third option of the trilemma, Sturm maintains that forms are not the kind of being that can be conceived of or exist independently from the being that they inform. Natural forms cannot be understood as a kind of substance or being intermediate between material and spiritual substances because forms are not substances in the first place. Since natural forms are relational beings they cannot be substances, and thus the very idea of a ‘substantial form’ is a chimera, a category mistake. The only viable option left is thus the one defended by Sturm himself: forms are modes of matter, and since matter is causally passive, forms are causally passive as well.