Suarez, Francisco. trans. Gracia, Jorge. Milwaukee, WI: Marquette University Press, 1982.
While his prose is incredibly technical and dense, the question before the house is quite straightforward: do I as an individual add anything to “human nature?’ Scotus said the individual adds a real mode to human nature. Nominalism says it adds nothing. Suarez argues that something real is added to human nature, but not of human nature. The individual adds a conceptual distinction.
A similar problem plagued Trinitarian discussions: if all three persons are God, then why isn’t the divine nature a fourth hypostasis? (The answer could only come by the doctrine of personal properties and eternal generation. Also, a person must be defined as a mode of the essence).
His argument hinges on the premise that that by which an entity is individualized is the same by which it is unified. Entity and unity are correlative. This makes sense. In the manner of a disputatio, Suarez works through the various options for how we can distinguish entities.
For example, quantity can’t be that by which we individuate something. Suarez says it is accidental and extrinsic to the entity. Quantity can only distinguish by place (Suarez 86). This is also the case because I can gain and lose matter yet still be an individual entity (think of the Ship of Theseus problem).
Towards a solution: Suarez hints that a combination of matter and form is the principle of individual unity (133). Form causes the specific difference, but individual form causes the individual difference. Very true, but I am not sure how clear the clause “individual form causes the individual difference” is. That seems true by definition. I think Suarez is back to his earlier claim that the individual form adds a “conceptual difference” (see translators note on p.137).
What is a “substantial form,” or why is it important?
Conclusion: the principle of entitas is matter, form, and union (section 6). The mode is the unity of matter and form.
Even by scholastic standards, this is an extremely difficult text. We give high praise to Jorge Gracias for lucid notes and a wonderful glossary of scholastic terms.