Mark asked:

How have immaterial forces like gravity, electro-magnetic force and atomic force been categorized in
philosophy? Are they considered as "extended in space"? What kind of reality do they have? Where
do they fit in a world composed of phenomena that can only be mental or physical in nature? I
suppose they would fit squarely on the physical side. What serious philosophers have questioned this
categorization? Are these forces a "third thing"? Forgive the scatter-shot approach, and many thanks
for your reply.

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Forces such as gravity and magnetism would undoubtedly be classified as physical. However, the
recognition of the existence of such forces (which, arguably, goes back to the first of the Presocratic
philosopher/ physicists Thales who invoked the examples of the magnet and rubbed amber as proof
that the power of 'the gods' resides in all things) poses a tricky problem.

When a magnet attracts iron filings, or when rubbed amber attracts cotton fibres, the filings, or the
fibres are causedto move. The concept of cause and effect is fundamental in making sense of our
experience. Without the 'cement' of causation, there would be no world, no universe. Kant argued that
there would not even be such a thing as 'experience'.

One central feature of causation, as it figures in our ordinary experience, is that object A can cause a
change in object B only through contact.The hammer strikes the nail, the stone shatters the glass.
Where there is a spatial gap, we look for some hidden structure that physically connects cause and
effect. When you hear a car backfire, the vibrations of air molecules carry the sound to your ear.
There can be no 'action at a distance'.

In that case, what are we to say about the apparent causal effects of the magnet and the rubbed
amber? These phenomena present a dilemma for the philosopher seeking to understand the nature
of causation:

*
Allow action at a distance. Reject the belief that a cause must be contiguous with its effect. One can
perhaps make some headway with the claim that this belief merely reflects our own anthropomorphic
prejudices. Experience teaches us that we can bring about changes in things only through contact: it
is the hallmark of irrationalism — 'magical thinking' — to suppose that you can bring about changes in
the world by reciting a spell or sticking a pin in a doll. But our experience is limited. If we went purely
by our experience, and not knowing the physical explanation for the transmission of sound, we ought
to regard it as 'magical' that anyone can hear us when we speak.

*
Retain the principle that a cause must be contiguous with its effect, and posit that the force of gravity
between two masses, or the force between a magnet and a piece of iron exists as a fieldwhose
nature can be known only through its effects. The iron filings which are attracted to the magnet are
constantly in contact with the 'magnetic field' which the magnet creates around it. The problem with
this alternative is that there is no way you can see gravitational or magnetic fields. Their existence is
purely hypothetical.

It is fair to say that this dilemma does not really exist for the contemporary physicist. There is no
credible alternative, the physicist will say, to the belief in the existence of fields. The choice is
between explanation and no explanation. Fields are indispensable as theoretical posits. The question
of how realista view one may take of such intrinsically unobservable entities remains one for the
philosopher.

Geoffrey Klempner

I think you have to be clearer about the terms you use. You talk as if physical and material mean the
same thing. Physical objects like chair and tables need not be material objects. For instance, George
Berkeley, the great 18th century Idealist who believe everything was mind-dependent (that is what
Idealism means) still believed there were chairs and tables (physical objects) but that they were
immaterial. Physical, for him, meant studied by physics, but he did not believe that physics was
committed to materialism. Quite the contrary, since he did not believe there were material objects but
did think there were physical objects (chairs and tables). He also thought that space was "ideal" i.e.
immaterial, (as, by the way, did Einstein).

What is mental might also be material. If the mind is (really) the brain, or the central nervous system,
then the mind is material because the brain or central nervous system is material. It depends on you
concept of mind. If, again, you are a behaviorist, then you think that the mind is understandable in
terms of actual and potential behavior. And the behavior is the behavior of a material thing, namely
the body.

What about electro-magnetic forces and the like? Well, they are certainly physical, for they are
studied by physics. But whether they are material is a different matter, if matter at all.

I used to know, but I don't recall who said "What is matter? Never mind. What is mind? Doesn't
matter." But it should be noted that possibly the foremost philosophical journal in Britain, "Mind" is
entered in the post office as "second class matter".

Kenneth Stern