# Discussions

Ghosts?

A famous critique of Descartes’ dualism was offered by Gilbert Ryle who held that we have no more idea of how the purely mental could move the physical than we can explain how a ghost could run a machine: if a ghost can pass through a wall then how can a ghost hand pull a lever?  To put this in physicalist terms, only a physical cause can bring about a physical event.  As if it’s clear what that might mean…

Are we really any more clear about physical causation?  When the cue ball hits the 8 ball and it rolls into the corner pocket, it seems obvious that the cue ball is the physical cause and the 8 ball rolling into the pocket.  But it’s not.  Imagine a cue ball made of Styrofoam and an 8 ball made of lead.  What would happen then?  Not much.  (And if we take this to the extremes, nothing at all happens.)  Not any old ball will move another.  It must be a sufficiently weighty ball.  But even that is not enough.  There is nothing logically odd about a normal cue ball hitting a normal 8 ball and stopping cold.  The only reason this is nomologically odd is that there is this thing called inertia.  So what is really moving the 8 ball is not another physical object, but rather an object with enough inertia.  And what, exactly, is inertia?  Well it is the tendency or disposition of an object to remain in motion if it is moving and to stay still if it is not moving unless acted upon by some external force.  This is where things get sticky.  Is inertia physical?  Are things like tendencies and dispositions—terms usually applied to mental states—legitimate members of a physical explanation?  And if not, then why are we so ready to say that a physical/physical causal relation is obvious and unproblematic compared to a mental/physical causal relation?  Truth is, there’s ghosts everywhere driving all sorts of machines.

### 3 Responses to Discussions

1. Mitzie Cly says:

Superb blog post, pretty much what I had been in search of.

2. Kae Barron says:

As I understand it, inertia is a property of matter. The law of inertia explains matter’s behavior when it is acted upon (propelled) by a physical force (energy). Thereafter, physical objects/substances or interactions (such as friction or impact) impede or fail to impede the object’s motion. To say that inertia is a ghost is like saying that an object’s weight is a ghost which causes it to fall. Gravity’s force, likewise, is not a ghost, but the interaction between matter and the “fabric” of space-time. Now, I don’t claim that the mind-brain problem has been completely and irrefutably explained/solved/understood by anyone; but I don’t see the requirement for “ghosts” in explaining or understanding physics.

• Discussion says:

But that’s just the issue… what, exactly is a property (as in a “property of matter”)? For example, “being red” is not a property of an apple (since redness is in our minds) so it must be something like the ABILITY to reflect a certain wavelength of light–since it would still be an apple in the dark. But to get rid of the ghostly term “ability,” we need to talk about a physical structure. What kind of structure? Well, whatever it is that causes us to see red.

Inertia doesn’t explain anything–it simply describes. We see that objects tend to stay in motion or at rest and we call this “tendency” inertia–but we still have no idea why objects act in this way, we just give a name to the phenomenon. Saying something falls because of gravity is nothing more than saying things drop because (we suppose) there is a thing-dropping force of some kind.

Physicians once referred to the somnolent property of certain drugs used to help people sleep as though they were explaining something. But in fact, all they were saying was that drugs which tend to make people sleepy have a sleep inducing property.

We talk just as easily about force and mass. But try to define “mass” without reference to “weight” or “weight” without reference to “mass.” What do you have beyond description? (And if Einstein is right, gravity is not a force at all.)

My point is just that there is a lot of hand waving going on; magic tricks. And the illusion of substance is… well, ghostly.