stence of sense-data derived from looking at
the print which gives the news. This knowledge scarcely rises into
consciousness, except in a person who cannot read easily. A child may be
aware of the shapes of the letters, and pass gradually and painfully to
a realization of their meaning. But anybody accustomed to reading
passes at once to what the letters mean, and is not aware, except on
reflection, that he has derived this knowledge from the sense-data
called seeing the printed letters. Thus although a valid inference from
the-letters to their meaning is possible, and _could_ be performed
by the reader, it is not in fact performed, since he does not in fact
perform any operation which can be called logical inference. Yet
it would be absurd to say that the reader does not _know_ that the
newspaper announces the King's death.

We must, therefore, admit as derivative knowledge whatever is the result
of intuitive knowledge even if by mere association, provided there _is_
a valid logical connexion, and the person in question could become aware
of this connexion by reflection. There are in fact many ways, besides
logical inference, by which we pass from one belief to another: the
passage from the print to its meaning illustrates these ways. These
ways may be called 'psychological inference'. We shall, then, admit such
psychological inference as a means of obtaining derivative knowledge,
provided there is a discoverable logical inference which runs parallel
to the psychological inference. This renders our definition of
derivative knowledge less precise than we could wish, since the word
'discoverable' is vague: it does not tell us how much reflection may be
needed in order to make the discovery. But in fact 'knowledge' is not a
precise conception: it merges into 'probable opinion', as we shall
see more fully in the course of the present chapter. A very precise
definition, therefore, should not be sought, since any such definition
must be more or less misleading.

The chief difficulty in regard to knowledge, however, does not arise
over derivative knowledge, but over intuitive knowledge. So long as we
are dealing with derivative knowledge, we have the test of intuitive
knowledge to fall back upon. But in regard to intuitive beliefs, it is
by no means easy to discover any criterion by which to distinguish
some as true and others as erroneous. In this question it is scarcely
possible to reach any very precise result: all our k