How often have I said to you," Sherlock Holmes observed to Dr. Watson, "that when you have eliminated the impossible, whatever remains, however improbable, must be the truth?" And how often do we need to be reminded that this is a maxim that is quite generally ignored by human beings?
Here is an immediate test to prove the point. Figure 1 shows a photograph
of a strange object, created some years ago in the laboratory of Professor
Richard Gregory. What do you see this as being
a picture of? What explanation does your mind construct for the data arriving
at your eyes?
You see it, presumably, as a picture of the so-called impossible triangle: that is, as a picture of a solid triangular object whose parts work perfectly in isolation from one another but whose whole refuses to add up-an object that could not possibly exist in ordinary three-dimensional space.
Yet the fact is that the object in the picture does exist in ordinary space. The picture is based on an unretouched photograph of a real object, taken from life, with no kind of optical trickery involved. Indeed, if you were to have been positioned where the camera was at the moment the shutter clicked, you would have seen the real object exactly as you are seeing it on the page.
What, then, should be your attitude to this apparent paradox? Should you perhaps (with an open mind, trusting your personal experience) believe what you unquestionably see, accept that what you always thought could not exist actually does exist, and abandon your long-standing assumptions about the structure of the "normal" world? Or, taking heed of Holmes's dictum, would you do better instead to make a principled stand against impossibility and go in search of the improbable?
The answer, of course, is that you should do the second. For the fact
is that Gregory, far from creating some kind of
"paranormal" object that defies the rules of 3-d space,
has merely created a perfectly normal object that
defies the rules of human
expectation. The true shape of Gregory's "improbable triangle" is revealed
from another camera position in Figure 2. It is, as it turns out, a most
unusual object (there may be only a couple of such objects in existence in
the universe). And it has been photographed for Figure 1 from a most unusual
point of view (to get this first picture, the camera has had to be placed
at the one-and-only position from which the object looks like this). But
there it is. And now that you have seen the true solution, presumably you
will no longer be taken in.
If only it were so! You look at Figure 2. And now you look back at Figure
1. What do you see this time around? Almost certainly, you still see exactly
what you saw before: the impossibility rather than the improbability! Even
when prompted in the right direction, you happily, almost casually, continue
to "make sense" of the data in a nonsensical way. Your mind, it seems,
cannot help choosing the attractively simple-even if mad- interpretation
over the unattractively complicated-even if sane-one.
Logic and common sense are being made to play second fiddle to a perceptual ideal of wholeness and completion.
There are many examples in the wider world of human politics and culture
where something similar happens, that is to say, where common sense gets
overridden by some kind of seductively simple explanatory principle- ethical,
political, religious, or even scientific. For, if there is one thing that
human beings are amazingly prone to (perhaps we might say good at), it is
in emulating the camera operator who took the photograph of Figure 1 and
manoeuvring themselves into just the one ideological position from which
an impossible, even absurd explanation of the "facts of life" happens to
look attractively simple and robust.
This special position may be called, for example, Christianity, or Marxism,
or Nationalism, or Psychoanalysis- maybe even some forms of science, or
scientism. It may be an ideological position that appeals only to some of
the human population some of the time or one that appeals to all of the
population all of the time. But, whichever it is, to those people who, in
relation to a particular problem, are currently emplaced in this position,
this will almost certainly seem to be the only reasonable place there is
to be. "Here I stand," in the words of Martin Luther, "I can do no other";
and the absolute rightness of the stance will seem to be confirmed by the
very fact that it permits the welcome solution to the problem that it does.
Yet the telltale sign of what is happening will always be that the solution
works only from this one position-and that if the observer were able to shift
perspective, even slightly, the gaps in the explanation would appear. Of
course, the trick-for those who want to keep faith and save appearances-is
not to shift position, or to pull rapidly back if ever so tempted. The lesson
is that when would-be gurus offer us final answers to any of life's puzzles,
a way of looking at things that brings everything together, the last word
on "How Things Are"-we should be watchful. By all means, let us say: "Thank
you, it makes a pretty picture." But we should always be prepared to take
NICHOLAS HUMPHREY is a theoretical psychologist who has held research and teaching posts at both Oxford and Cambridge, as well as fellowships in the United States and in Germany. His books include Consciousness Regained and The Inner Eye, as well as A History of the Mind. His interests are wide ranging: He studied mountain gorillas with Dian Fossey in Rwanda; made important discoveries about the brain mechanisms underlying vision; proposed the now- celebrated theory of the "social function of human intellect"; and is the only scientist ever to edit the literary journal Granta. He has been the recipient of several honours, including the Martin Luther King, Jr., Memorial Prize in 1985.
How Things Are: A Science Toolkit for the Mind