External reality

As I look around the room where I am now sitting I see various objects. That is, through the lenses in my eyes, through the structure
of the retina, through assorted electrical impulses received in
my brain, etc, I experience sensations of colour and shape which
I interpret as being caused by objects outside myself. These objects
form part of what I call the ‘real world’ or the ‘external reality’.
That such a reality exists, independent from my observation of it,
is an assumption. The only reality that I know is the sensations of
which I am conscious, so I make an assumption when I introduce
the concept that there are real external objects that cause these sensations.
Logically there is no need for me to do this; my conscious
mind could be all that there is. Many philosophers and schools of
philosophy have, indeed, tried to take this point very seriously
either by denying the existence of an external reality, or by claiming
that, since the concept cannot be properly defined, proved to exist,
or proved not to exist, then it is useless and should not be discussed.
Such views, which as philosophic theories are referred to by words
such as ‘idealism’ or ‘positivism’, are logically tenable, but are
surely unacceptable on aesthetic grounds. It is much easier for me
to understand my observations if they refer to a real world, which
exist even when not observed, than if the observations are in
fact everything. Thus, we all have an intuitive feeling that ‘out
there’ a real world exists and that its existence does not depend
upon us. We can observe it, interact with it, even change it, but we
cannot make it go away by not looking at it. Although we
can give no proof, we do not really doubt that ‘full many a flower
is born to blush unseen, and waste its sweetness on the desert
air’.

It is important that we should try to understand why we have this
confidence in the existence of an external reality. Presumably one
reason lies in selective evolution which has built into our genetic
make-up a predisposition towards this view. It is easy to see why
a tendency to think in terms of an external reality is favourable to
survival. The man who sees a tree, and goes on to the idea that
there is a tree, is more likely to avoid running into it, and thereby
killing himself, than the man who merely regards the sensation of
seeing as something wholly contained within his mind. The fact of
the built-in prejudice is evidence that the idea is at least ‘useful’.
However, since we are, to some extent, thinking beings, we should
be able to find rational arguments which justify our belief, and
indeed there are several. These depend on those aspects of our experience which are naturally understood by the existence of an
external reality and which do not have any natural explanation
without it. If, for example, I close my eyes and, for a time, cease
to observe the objects in the room, then, on reopening them, I see,
in general, the same objects. This is exactly what would be expected
on the assumption that the objects exist and are present even when
I do not actually look at them. Of course, some could have moved,
or even been taken away, but in this case I would seek, and
normally find, an explanation of the changes. Alternatively I could
use different methods of ‘observing’, e.g. touch, smell, etc, and I
would find that the same set of objects, existing in an external
world, would explain the new observations. Thirdly, I am aware
through my consciousness of other people. They appear to be
similar to me, and to react in similar ways, so, from the existence
of my conscious mind, I can reasonably infer the existence of real
people, distinct from myself, also with conscious minds. Finally,
these other people can communicate to me their observations, i.e.
the experiences of their conscious minds, and these observations
will in general be compatible with the same reality that explains my
own observations.
In summary, it is the consistency of a vast range of different
types of observation that provides the overwhelming amount of
evidence on which we support our belief in the existence of an
external reality behind those observations. We can contrast this
with the situation that occurs in hallucinations, dreams, etc, where
the lack of such a consistency makes us cautious about assuming
that these refer to a real world.

We turn now to the scientific view of the world. At least prior
to the onset of quantum phenomena this is not only consistent
with, but also implicitly assumes, the existence of an external
reality. Indeed, science can be regarded as the continuation of the
process, discussed above, whereby we explain the experiences of
our senses in terms of the behaviour of external objects. We have
learned how to observe the world, in ever more precise detail, how
to classify and correlate the various observations and then how to
explain them as being caused by a real world behaving according
to certain laws. These laws have been deduced from our experience,
and their ability to predict new phenomena, as evidenced by the
enormous success of science and technology, provides impressive support for their validity and for the picture of reality which they
present.

This beautifully consistent picture is destroyed by quantum
phenomena. Here, we are amazed to find that one item, crucial to
the whole idea of an external reality, appears to fail. It is no longer
true that different methods of observation give results that are consistent
with such a reality, or at least not with a reality of the form
that had previously been assumed. No reconciliation of the results
with an acceptable reality has been found. This is the major revolution
of quantum theory, and, although of no immediate practical
importance, it is one of the most significant discoveries of science
and nobody who studies the nature of reality should ignore it.
It will be asked at this stage why such an important fact is not
immediately evident and well known. (Presumably if it had been
then the idea of creating a picture of an external reality would
not have arisen so readily.) The reason is that, on the scale
of magnitudes to which we are accustomed, the new, quantum
effects are too small to be noticed. We shall see examples of this
later, but the essential point is that the basic parameter of
quantum mechanics, normally denoted by f~ (‘h bar’) has the
value 0.OOO OOO 000 OOO OOO OOO OOO OOO 001 (approximately) when
measured in units such that masses are in grams, lengths in
centimetres and times in seconds. (Within factors of a thousand or
so, either way, these units represent the scale of normal experience.)
There is no doubt that the smallness of this parameter is
partially responsible for our dimculty in understanding quantum
phenomena-our thought processes have been developed in situations
where such phenomena produce effects that are too small to
be noticed, too insignificant for us to have to take them into
account when we describe our experiences.