How can truly abstract objects be causal? (George F. R. Ellis video interview)

[Yazata]

SEP: "The contemporary distinction between abstract and concrete is not an ancient one. Indeed, there is a strong case for the view that, despite occasional exceptions, it played no significant role in philosophy before the 20th century. The modern distinction bears some resemblance to Plato’s distinction between Forms and Sensibles. But Plato’s Forms were supposed to be causes par excellence, whereas abstract objects are generally supposed to be causally inert."

I guess that in Plato (even more in Plotinus and the Neoplatoninsts), the ultimate and inconceivable Source and the ideal forms that emanated from it were the higher realities, while the physical world was a flawed and imperfect image of what is even more real than the physical world. It was very much a theory of metaphysical levels.

While today's abstract objects are more along the lines of mental constructs, created by us by taking various aspects of reality that are of interest to us, and removing them from their context.

In the former version, the higher ideal planes are the source of causal action (formal cause, final cause particularly). We see echoes of that today in theoretical physics that often seem to me to believe that their arcane mathematical apparatus explain and control what happens here on the physical plane.

In the latter version, I don't know that abstractions have causal powers. It's more that the physical realities from which the abstractions are abstracted are the locus of causality. So we can take a real life physical situation and think of it in terms simply of masses in motion, and make predictions about those motions without worrying about what the masses are.

If we argue that what matters causally are the motions and the masses, then we might be leaning in the Neoplatonist direction, by according the abstractions a higher metaphysical status that controls and determines the situation.

[Magical Realist]

I think abstract objects and ideas can have a causal effect on physical reality. But since they are outside of time and space, it would be a very different kind of causality from physical causation. Take the abstract object or idea of "humanity" or "humanness". As a specific member of the human species, I participate or share in this abstraction in my very nature. The qualities that make up being human are instantiated in my body and my brain and my mind. The idea of humanity does not cause me to do things I would not otherwise do exactly. Rather it manifests itself as the essence or "whatness" of who I am--the 6 million year old substrate from which I draw all the possibilities and tendencies of my being. Abstract objects "cause" physical events to happen by defining both the possibilities and limitations of what can happen and how it can happen.