Rodrigo de Arriaga’s Substance Trialism

According to Jesuit philosopher and theologian Rodrigo de Arriaga (1592–1667), form and matter as well as the composite made up of them are all unequivocally substances. Hence, we have in Arriaga a “substance trialism.” As for matter, Arriaga follows in the footsteps of his Jesuit predecessors Francisco Suárez (1548–1617) and Pedro Hurtado de Mendoza (1578–1641) in assigning to it its own essence and its own, independent existence. Further, matter is identical to quantity, according to Arriaga, and he even sometimes calls quantity a “substance,” therefore. Notwithstanding this, Arriaga speculates about what matter without quantity would be like. These speculations, together with other considerations, lead him to the view that matter has a point-like structure, and that a continuum is constituted by a finite number of indivisible parts. As for form, Arriaga considers the generation of forms of material things to be distinct from their union with matter, which results in a great number of possibilities as to how form and matter may be interrelated. When it comes to the composite, finally, something has to come over and above form and matter in order for these to constitute a whole. This is the union, which is considered to be a mode in Arriaga’s metaphysics. The union is only one single mode, but still belongs to the form and to matter equally, making this what has been called a “straddling” mode.