The interaction problem for Naturalism

The interaction problem for immaterialism is something like this:

1.) Natural bodies act only by interacting with what moves them.

2.) Natural things cannot interact with the non-physical. therefore etc.

While widely viewed as an intractable problem, its premises seem to cut both ways. If natural bodies move only by interacting by other bodies, then  A only acts because it interacts with B, B can only acts because it interacts with C, and so on ad infinitum. But such an account contradicts itself: on the one hand it continually posits causes in order to sufficiently account for the action while at the same time insisting that it is impossible for such continual positing to sufficiently explain anything.

But it’s not necessary to insist on this point since its uncontroversial to insist that lines of natural causality are finite. Classical physics drifted into thinking that motion reduced to a first mover like gravity, which came to be seen as a tugging power that enveloped and instantly collapsed all bodies toward each other,* and we later thought of energy as a single motive reality that leaps from one natural body to another, exhausting the motion of one thing before leaping out of the body, totally preserved, and causing motion in a new way.

But we can’t make classical gravity or energy a source of action in physical things and insist on premise (1)above. The moon, for example, doesn’t interact with classical gravity, nor does energy interact with the bodies it moves. There is no surface contact, no mechanism, nor does the mass of the body somehow need to “come in contact with” the ghostly tugging power of classical gravity. But why insist on this? There doesn’t seem to be any theory of physics, ever, that insisted that all action was the result of interaction. Physics always posits some non-interactive force at the foundation of physical action: Aristotle had his 57 mover gods of the celestial bodies, the classical era had gravity (supplemented by whatever divine action was needed to keep gravity from collapsing everything into a heap) we have mass-energy and every other sort of agency that falls under a conservation law.

So not only is premise (1) of the interaction argument false, but no major physical theory has ever thought it was true. It has never done any actual scientific work, and to accept it is an impediment to having a physical system at all. The interaction argument is rather an attempt to articulate a subtle shift that classical physics made in the account given of fundamental, non interactive forces. Physics has always seen these fundamental movers as eternal and executing predicable motions (which is why Ptolemy could write a mathematical astronomy even while thinking that the planets were moved by the gods) but the shift in our time is to see these eternal, ageless, non-interactive agencies as impersonal or necessarily unintelligent. The non-interactive agencies must be – to use the mysterious adjectives we spontaneously applied to them – blind or brute Needless to say, this is a judgment that is no more and no less scientific (or mythological) than calling them gods or angels.

*This happened in spite of Newton’s insistence that gravity was not a tugging force, and to assume that it was made it an occult quality. But in this sense the tradition was more logical than Newton: what moves first must be non-interactive and given what gravity explained, it made sense to assume that it was just such a force.

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