boys and weather-cocks, that is to say,
when--

(a) It gives different responses to stimuli which differ in relevant
ways;

(b) It gives the same response to stimuli which do not differ in
relevant ways.

What are relevant ways depends upon the nature and purpose of the
instrument. In the case of a weather-cock, the direction of the wind is
relevant, but not its strength; in the case of the boy, the meaning of
the words of your question is relevant, but not the loudness of your
voice, or whether you are his father or his schoolmaster If, however,
you were a boy of his own age, that would be relevant, and the
appropriate response would be different.

It is clear that knowledge is displayed by accuracy of response to
certain kinds of stimuli, e.g. examinations. Can we say, conversely,
that it consists wholly of such accuracy of response? I do not think
we can; but we can go a certain distance in this direction. For this
purpose we must define more carefully the kind of accuracy and the kind
of response that may be expected where there is knowledge.

From our present point of view, it is difficult to exclude perception
from knowledge; at any rate, knowledge is displayed by actions based
upon perception. A bird flying among trees avoids bumping into their
branches; its avoidance is a response to visual sensations. This
response has the characteristic of accuracy, in the main, and leads
us to say that the bird "knows," by sight, what objects are in its
neighbourhood. For a behaviourist, this must certainly count as
knowledge, however it may be viewed by analytic psychology. In this
case, what is known, roughly, is the stimulus; but in more advanced
knowledge the stimulus and what is known become different. For example,
you look in your calendar and find that Easter will be early next year.
Here the stimulus is the calendar, whereas the response concerns the
future. Even this can be paralleled among instruments: the behaviour of
the barometer has a present stimulus but foretells the future, so that
the barometer might be said, in a sense, to know the future. However
that may be, the point I am emphasizing as regards knowledge is that
what is known may be quite different from the stimulus, and no part of
the cause of the knowledge-response. It is only in sense-knowledge that
the stimulus and what is known are, with qualifications, identifiable.
In knowledge of the future, it is obvious that they are totally
distinct, si