erefore, that we are driven to a different kind of
definition. It is for this reason that it was necessary to develop
the definition of perception. With this definition, we can define a
sensation as the non-mnemic elements in a perception.

When, following our definition, we try to decide what elements in our
experience are of the nature of sensations, we find more difficulty
than might have been expected. Prima facie, everything is sensation that
comes to us through the senses: the sights we see, the sounds we hear,
the smells we smell, and so on; also such things as headache or the
feeling of muscular strain. But in actual fact so much interpretation,
so much of habitual correlation, is mixed with all such experiences,
that the core of pure sensation is only to be extracted by careful
investigation. To take a simple illustration: if you go to the theatre
in your own country, you seem to hear equally well in the stalls or the
dress circle; in either case you think you miss nothing. But if you go
in a foreign country where you have a fair knowledge of the language,
you will seem to have grown partially deaf, and you will find it
necessary to be much nearer the stage than you would need to be in your
own country. The reason is that, in hearing our own language spoken, we
quickly and unconsciously fill out what we really hear with inferences
to what the man must be saying, and we never realize that we have not
heard the words we have merely inferred. In a foreign language, these
inferences are more difficult, and we are more dependent upon actual
sensation. If we found ourselves in a foreign world, where tables looked
like cushions and cushions like tables, we should similarly discover how
much of what we think we see is really inference. Every fairly familiar
sensation is to us a sign of the things that usually go with it, and
many of these things will seem to form part of the sensation. I remember
in the early days of motor-cars being with a friend when a tyre burst
with a loud report. He thought it was a pistol, and supported his
opinion by maintaining that he had seen the flash. But of course there
had been no flash. Nowadays no one sees a flash when a tyre bursts.

In order, therefore, to arrive at what really is sensation in an
occurrence which, at first sight, seems to contain nothing else, we have
to pare away all that is due to habit or expectation or interpretation.
This is a matter for the psychologist, and by