completely dependent upon the inductive principle as are the beliefs of
daily life All such general principles are believed because mankind have
found innumerable instances of their truth and no instances of their
falsehood. But this affords no evidence for their truth in the future,
unless the inductive principle is assumed.

Thus all knowledge which, on a basis of experience tells us something
about what is not experienced, is based upon a belief which experience
can neither confirm nor confute, yet which, at least in its more
concrete applications, appears to be as firmly rooted in us as many
of the facts of experience. The existence and justification of such
beliefs--for the inductive principle, as we shall see, is not the only
example--raises some of the most difficult and most debated problems of
philosophy. We will, in the next chapter, consider briefly what may be
said to account for such knowledge, and what is its scope and its degree
of certainty.

CHAPTER VII. ON OUR KNOWLEDGE OF GENERAL PRINCIPLES

We saw in the preceding chapter that the principle of induction, while
necessary to the validity of all arguments based on experience,
is itself not capable of being proved by experience, and yet is
unhesitatingly believed by every one, at least in all its concrete
applications. In these characteristics the principle of induction does
not stand alone. There are a number of other principles which cannot be
proved or disproved by experience, but are used in arguments which start
from what is experienced.

Some of these principles have even greater evidence than the principle
of induction, and the knowledge of them has the same degree of certainty
as the knowledge of the existence of sense-data. They constitute the
means of drawing inferences from what is given in sensation; and if what
we infer is to be true, it is just as necessary that our principles
of inference should be true as it is that our data should be true. The
principles of inference are apt to be overlooked because of their
very obviousness--the assumption involved is assented to without our
realizing that it is an assumption. But it is very important to realize
the use of principles of inference, if a correct theory of knowledge
is to be obtained; for our knowledge of them raises interesting and
difficult questions.

In all our knowledge of general principles, what actually happens
is that first of all we realize some particular application of