Spinoza on Parallelism and the Ontology of Thought

In this dissertation, I investigate whether Spinoza can consistently maintain his doctrine of parallelism while acknowledging the existence of four distinct types of ideas. Parallelism asserts a strict one-to-one correspondence between each idea and its object, establishing an isomorphic structure between the mental and physical worlds. This doctrine carries four implications: (1) the number of modes under each divine attribute must be equal, (2) each idea necessarily corresponds to and must be true of its object, (3) every idea must represent an external object, and (4) each idea and its object are one and the same thing, conceived under different attributes. Despite these implications, Spinoza’s system also acknowledges the existence of four types of ideas that appear to challenge them: ideas of ideas, which seem to multiply the number of modes under the attribute of thought; false ideas, which suggest that not all ideas correspond truthfully to their objects; beings of reason, which have no corresponding object outside the intellect; and the idea of God, which, if identical to its object, threatens to collapse the fundamental distinction between substance and mode. This dissertation systematically examines these challenges and demonstrates how the existence of the four types of ideas can be reconciled with parallelism. Drawing on Spinoza’s theories of distinctions and representation, I argue that the metaphysical structure of ideas allows for the unity of ideas and the ideas representing them without violating the numerical balance of modes across divine attributes. Furthermore, I show that Spinoza’s account of error, beings of reason, and the idea of God align with parallelism when properly understood. By resolving these tensions, this dissertation advances a more comprehensive understanding of Spinoza’s parallelism and sheds light on the character of Spinoza’s metaphysical system as shaped by this commitment.