What is Spinoza’s mind-body parallelism?
Answer by Billy Wheeler
Spinoza’s mind-body parallelism is an attempt to explain how the mind and body “seem” to interact if the mind and body are made of distinction substances. This is effectively a problem for dualist theories of mind and first comes up in Elizabeth of Bohemia’s letters to Descartes. He took it for granted that a physical body and a non-physical mind could interact. However, if the mind is as he says “non-extended” then it cannot really come into contact with the body. And as Elizabeth makes clear, most causal interactions involve some kind of physical contact.
Spinoza doesn’t address quite the same problem as Descartes, because for Spinoza there is only one substance: God. Nonetheless, mind and body are different attributes of this one substance. In reality there are no causal interactions between them: there is only the appearance of causal interaction. This is because God has made it so that every instance of a mental attribute is “matched” or “paired” with a bodily attribute. Hence their parallel occurrence.