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Next: 6. Actuality
Up: Philosophy of Nature and
Previous: 4.4 The Problem of
5. Reconsidering Philosophical Foundations
As we saw in chapter
4,
a considerable variety of methods have been used in attempting to
understand what quantum mechanics is really about. Some of these methods
have used the existing mathematical frameworks as starting points, and
have attempted to interpret it in ways that seem intelligible. Entities
such as events, particles or waves are postulated to exist, and to have
properties which are compatible with the existing rules of quantum
mechanics. Their properties are rather strange from the common-sense point
of view, but they have been seriously put forward as descriptions of what
the quantum world is really like.
An alternative approach starts not from existing physical theories, but from
some general considerations about what could possibly exist.
This approach is less closely connected with specific physical theories,
but does make extensive connections with the endeavours of philosophers
over the centuries to consider `what exists' in a general sense.
These two different approaches are manifest in the career of A.N.
Whitehead. To start with he was concerned with constructing an ontology of
events, in order to make sense of Einstein's Special Theory of
Relativity, and published books such as The Concept of Nature
(Whitehead [1920]) Later, however, he turned to a more philosophical
approach, and attempted to frame what he called a `coherent, logical
and necessary system of general ideas' in order to give a account
within the philosophy of nature of what the world could be like. His
Process and Reality (Whitehead [1929]) of this period is
therefore not closely related to the relativity and quantum theories which
were concerning the physicists of his day, but provided a much more
general framework of ideas by means of which specific physical
theories could be formulated.
His philosophy of nature in fact had less influence than he hoped, but
physicists such as Stapp [1977] have found them a useful starting point in
the investigation of quantum processes.
What I am attempting here is to frame a coherent and logical system of
general ideas in Whitehead's sense, but we do not end up with the same
system as he did. The main difference can be attributed to the greater
importance I give to dispositional properties and to potentialities.
Before we come to potentialities and dispositions, however, it is convenient
to begin our investigations with a determination of what actually
exists. Because we are sensitive to the problems of dispositions, etc., the
next chapter will try to determine what can exist in a full and primary sense
of actuality, a sense which excludes all potentialities and possibilities.
A Realist Philosophy of Nature
I begin by assuming, rather generally, that there are in our changing
world various particular and concrete things. Most of these
will be independent of ourselves, so we say they are part of nature,
rather than parts of our own mind. It is assumed, again, that each such
particular has a certain set of characteristics or properties, or some
form or other, which describes what they are, and distinguishes them from
among themselves. We do not exclude the possibility that each
particular's set of properties can be known by us in principle, and
quite possibly in practice too.
To know the whole character of a particular concrete thing in our changing
world, is to know its nature. This describes both what sort of
thing it is, and also the sources of any changes it may cause or undergo.
The nature of a particular is itself independent of our knowing, for it is
the real internal constitution in, and the source of real change of, that
particular. Change is an essential part of the natures of the particulars
which are considered in this book. These particulars are therefore
physical or natural existents, as opposed, for example, to the unchanging
formal entities of logic and mathematics (whatever they may turn out to
be). The present philosophy of nature seeks a clear understanding of
change and causality, and how these occur in natural particulars.
We must therefore call into question Hume's attitude to the problems of
causality and change. His attitude is to allow problems of epistemology to
dictate the kind of things which are thought to exist, but we are not
forced to accept this dictation. It is possible to pursue a distinctly
non-Humean course5.1, and investigate, in general terms, the natures of particulars and
the powers therein for change. Parallel with our different approach, we
must reject Hume's ontology in which there exist only momentary events
with no intelligible causal connections. It is also necessary, as will be
discussed in the next chapter, to avoid commitment to any account of the
relation between formal logic and set theory which denies the possibility of
real change for particulars.
The way we get around Hume's problems is to adopt a
hypothetico-deductive approach. That is, we hypothesise the
characters of certain entities which could exist, and follow
out deductively the consequences of that hypothesis. Only later do we
consider what might have these characters, or indeed whether
anything at all has the characters we hypothesised. There are
therefore deductive and necessary connections within the theory being
proposed, but only empirical and contingent connections of the theory with
the real world.
This follows exactly the `conjectural essentialism' scheme that in
section 2.6 was found most satisfactory to describe natural
dispositions and physical laws.
This means that the arguments in the next two chapters are rather general,
and should be valid whatever in the physical world in facts turns
out to be actual and potential. It is only in chapter
8
that specific instantiations are proposed for some of the general
concepts. It is perhaps thereby rather frustrating to the impatient
reader, who finds it difficult to imagine to himself exactly what is going
on, but similar problems arise whenever mathematical or logical proofs are
being presented.
In a sense, we are here developing a `process logic' which should
have a number of distinct fields of application as well as our target
application in the interpretation of quantum physics.
I will in fact exploit the uncertainty of application in the order of
arguments in the following chapters. Chapters
8
(and those following) will assume a specific identification of `what
is actual', namely as past events at points in space-time.
This, however, will turn out to be not that best suited for the
world described by quantum physics. That identification, however, provides
a simple and easily-understood model for a kind of quantum
world, so I will use it to illustrate and clarify the basic concepts at
issue. Only in chapter
11
will this (contingent) identification be replaced by another, namely that
what is actual are past selections at points in a tree-like structure of
alternatives. Since, though, the arguments in our `process logic'
have general validity, we can carry over many of our previous conclusions
to the more complete model.
Next: 6. Actuality
Up: Philosophy of Nature and
Previous: 4.4 The Problem of
Prof Ian Thompson
2003-02-25
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