|
| |
Next: 2. Dispositions
Up: Philosophy of Nature and
Previous: Contents
1. Prospects for a Philosophy of Nature
In the Twentieth Century, despite the advances of modern science, we are
no longer sure what the world is made of. We are confident that it is
made out of parts of various kinds, but it has become
mysterious what these parts are made of.
If we ask the question, `what is it to be a substance?', we might
first turn to scientists for an answer, to physicists in particular. A
physicist will explain how all kinds of ordinary matter are composed of
small atoms, which are composed of electrons, protons, and neutrons.
Protons and neutrons are again composed of quarks, he says he believes,
but when pressed as to what really are electrons and quarks, he
says that he can tell you how they behave, but that he
doesn't really know what they are. If he is feeling unkind,
he might say `that is a meaningless question', otherwise he
will say that the electrons and quarks seem to be some kind of `ultimate
particles' whose existence and behaviour you just have to take on trust.
`You have to start somewhere', he might add.
But when we asked the initial question, `what is it to be a
substance?', in a sense we were going straight to the question of these
`ultimate particles'. We want to know what the world is really made
of, and what are the ultimate individuals in the physical world.
We have a feeling that we can't go on looking for smaller and smaller
constituents ad infinitum. The process of subdivision should
ultimately come to a stop with the `real individuals' that are the real
substances of the world. We don't know for certain if physics
has yet reached the stage of looking at these ultimate substances. Of
course, physicists almost always believe they have come to that
stage, but that might just be because they haven't yet done the right kind
of experiment.
This means that if we want to know what these ultimate substances might be
like, we have to turn to philosophy rather than to physics. We will then
have to be satisfied with general principles rather than particular
knowledge, because philosophers can only argue from general considerations
about what is possible, and do not provide detailed knowledge about what
actually occurs in particular circumstances. You may think that
consideration of `mere possibilities' will not be fruitful, but you would
be forgetting that every scientific theory presupposes some
general framework about what is possible. Different scientific theories go
along with different philosophical frameworks about what our ultimate
substances might be like. The physical theories of the Greeks, of Newton
and of modern quantum physics assume different philosophical
ideas about substances, and these ideas are not compatible with each
other. They cannot all be correct! My purpose in this book is to
illuminate these different basic ideas, and to see whether there is one
set of ideas which recommend themselves as reasonable, and which can help us
understand the world and its peculiarities as revealed by quantum physics.
It is largely because of the difficulties in understanding modern quantum
physics that many people have realised to need to re-examine the
foundations of physics. As a result of quantum mechanics, questions have
been continually raised concerning some of the deepest questions in
philosophy, such as whether the world exists independently of our
observations or of our minds, whether physical substances exist and/or
have any definite properties, whether these properties (should they exist)
are in any way knowable, and whether indeed anything could be
said to have definitely happened to the exclusion of its alternatives.
Many, in a kind of agnosticism, have despaired of positive answers to
these questions ever being found1.1, and others have turned to philosophies where it is accepted that
`objective reality' is altogether an ephemeral by-product, or an illusion
of some kind1.2.
When, therefore, we do reconsider foundations, we are almost overwhelmed
by the enormous range of physical theories and natural worlds that are
logically possible.
Reece [1973], Jammer [1974] and Herbert [1985] survey some (but not all!)
of this range. Rather than being lost in the maze of science-fiction-like
realms, a better approach would be to think more carefully about the
collection of general ideas which we bring to bear when we look
at nature. Traditionally, these have been the four ``ultimate'' concepts
used to characterise nature: matter, motion, time and space.
Leibniz was the first to point out the inadequacies in these four
``ultimates'', and how the first (`matter') was not essentially related to
the other three. (We will be looking in more detail at these notions of
classical physics in chapter
3.)
His was merely the beginning of a long line of critiques of the ideas of
physics, pointing out that the basic concepts of many theories are not
properly consistent with each other. It is of course possible to argue
`that even the ideals of clarity and consistency can be legitimately
compromised in order to obtain other advantages'
(Edwards [1985]), but this can at best be only a temporary manoeuvre. It
is only after careful consideration of the ultimate concepts we use, and
the finding of a consistent set, that we can have any confidence in them
as realistic descriptions of nature.
The kind of discussions here can best be called the philosophy of nature.
This term is not in popular use, but it is needed in order to distinguish
our endeavours from the philosophy of science, and from the philosophy
of knowledge.
In the philosophy of nature we are going to consider ontological problems
directly, and not let them be obscured by questions of methodology and
epistemology. That is, we are going to pose and answer questions about
what exists, and not be side-tracked into questions of `how can
we be sure of that?', or of `how should we discover what exists in this
test-tube?'. In doing this, we want to take a realistic view of our
theories, at least, that is, when they have been considered carefully and
found consistent and adequate. We are not taking a merely
`instrumentalist' view of theories, whereby their only use is to enable
correct predictions. Nor are we taking a merely `phenomenological' view of
theories, whereby their only use is to describe our observations and
experimental results as does a map. Of course, if a theory is realistic
and correct, it will enable both correct predictions and accurate
descriptions: these tasks are non-trivial and are still important!
We may picture our theories as maps of reality. If our maps of reality
were comprehensive and consistent with each other, there would be little
demand for further investigations in the philosophy of nature. The
problem, in modern times, is precisely that our maps are fragmented,
confused, and often appear to contradict each other. Physicists survive
in this situation by marking various regions with large `Keep Out' signs,
and learning to choose which of their opposing maps should be used in the
various stages of their travels.
Richard Feynman [1967], for example, writes
I think it is safe to say that no one understands quantum mechanics.
 Do not keep saying to yourself, if you can possibly avoid it,
`But how can it be like that?' because you will get `down the drain' into
a blind alley from which nobody has yet escaped. Nobody knows how it can
be like that.
These practices and warnings seem more akin, however, to that of the
medieval cartographers when they wrote `here be dragons'. Feynman may well
have a point about the difficulties and dangers in trying to answer the
question `What can the world be like such that quantum mechanics can be
true of it?', but what we need therefore are suitable new instruments of
analysis which are precise and versatile. We will need to extend many of
our common sense ideas beyond their original scope, while at the same time
always considering carefully exactly how they can still be applied.
The Philosophy of Nature
The method adopted in this book is explicitly hypothetical and deductive,
rather than being an analysis either of our phenomenal experiences, or of
contemporary scientific theories. I will hypothesise the existence of
various things (`actual particulars' and `propensity fields', as they will
be called), and then the consequences of these will be drawn out in a
deductive fashion. In any hypothesising, however, I do not proceed
randomly.
Both the direction and aims of much of this book are strongly influenced
by Ivor Leclerc's excellent investigations (Leclerc [1972], [1986]) of the
many past accounts in the philosophy of nature that have been put forward
in the history of Western philosophy. He has been useful in providing
critical reassessments of the fundamental issues involved in our realistic
understanding of the nature of the physical world. His historical
perspectives are as valuable as his re-examination of the root problems
which have recurred almost unfailingly through the history of the
philosophy of nature. The most common problems are those of clarifying,
distinguishing and then relating the categories of
- actual vs. potential vs. possible,
- infinite vs. finite,
- continuity vs. discreteness,
- becoming vs. being,
- substance vs. form vs. act, and
- simple vs. compound.
It is from suggestions in his work that I derived my initial hypotheses
concerning actualities and potentialities. What I am now trying to do is
to present these concepts and their relations in a coherent whole. I will
be analysing in more detail the categories of actuality and potentiality,
and hope to flesh out the resulting categorical framework so that it has
consequences of any detailed science of nature.
The category of dispositions and potentialities is
the single most important category that must be considered anew. Science
has always had a kind of love-hate relation with properties in this
category, accepting their necessity and usefulness, but refusing to live
happily with them.
In general, it is modal properties of all kinds that cause
problems. These properties deal with what might happen, and,
despite their apparent remoteness and seeming unreality, we will see in
the next few chapters that they have an essential role in all kinds of
scientific investigations. Although various ideas of potentialities and
propensities have been proposed to help solve difficulties in physics,
they have been criticised as being too vague.
Hooker1.3, for example, remarks that this ``approach to quantum theory must
inevitably prove less than satisfying. Any theory whatever, so
far as I can see, could have its problems `solved' by this approach
-- simply because the concept of an `actualisation' of a `potential'
is so vague and intrinsically not open to direct investigation of its
structure.'' My aim in this book is therefore to see how potentialities
etc. can be understood sufficiently precisely, and then how
potentialities and dispositions can be fitted into a broad realistic view
of the world.
It may be objected that I really seem to be doing speculative physics all
along (or, that if not, I ought to be), but that would be to misunderstand
the relation between science and the philosophy of nature. It has been
remarked that quantum physics is not itself a physical theory, since it
does not specify any particular laws for potentials: rather, it is a
methodological and mathematical framework in which one can formulate
physical theories. Similarly, the philosophy of nature is not itself a
scientific theory (either methodologically or mathematically), but rather
a framework in which quantum theories can be formulated and interpreted
realistically. The task of the philosophy of nature is to provide a
general scheme for what can reasonably be said both to exist and to be
subject to change. Quantum theories then select some specific scheme, with
particular laws of change in specific kinds of spaces.
As a consequence of quantum physics it has often been said that we have to
give up any hope of a pictorial, literal or realistic description of what
goes on in the micro-world of atomic phenomena. We seem at best to have
only metaphorical and/or mathematical descriptions, without any clear idea
of the reality to which they refer. Sometimes we are told1.4
that certain ideas (e.g. those of classical physics), while necessary for
all our knowledge, are in fact false. At other times, it is contended that
``quantum physics conflicts with the ontological form of thought''1.5.
I will be arguing, instead, that the lack of literal and realistic ideas
betrays more a lack of imagination than a lack in reality. It ought to be
possible to interpret some ideas realistically, as being
unequivocally and literally true -- once (of course) we have ideas
which are good enough. We ought to be able to find ideas that we can
interpret literally, and not be forced forever to resort to ideas based
merely on mathematical formalisms or metaphors.
One important aim is to formulate a description of the world of relativity
and quantum physics that is independent of classical physics,
so that we can bypass some of the unwanted legacies which have accumulated
from the theories of material corpuscles. The task of this book is to
produce a formulation in sufficient detail that an understanding of
quantum physics begins to be possible. Even though the present
investigations will not produce a complete physical theory, I hope to show
that they are still valuable in providing some general ideas which are
reasonable, which can be realistically interpreted, and which contribute
in some part to our understanding of the world we live in and its quantum
peculiarities.
Next: 2. Dispositions
Up: Philosophy of Nature and
Previous: Contents
Prof Ian Thompson
2003-02-25
|
