refore, may also be
described as the world of being. The world of being is unchangeable,
rigid, exact, delightful to the mathematician, the logician, the builder
of metaphysical systems, and all who love perfection more than life. The
world of existence is fleeting, vague, without sharp boundaries,
without any clear plan or arrangement, but it contains all thoughts and
feelings, all the data of sense, and all physical objects, everything
that can do either good or harm, everything that makes any difference to
the value of life and the world. According to our temperaments, we shall
prefer the contemplation of the one or of the other. The one we do not
prefer will probably seem to us a pale shadow of the one we prefer, and
hardly worthy to be regarded as in any sense real. But the truth is that
both have the same claim on our impartial attention, both are real,
and both are important to the metaphysician. Indeed no sooner have we
distinguished the two worlds than it becomes necessary to consider their
relations.

But first of all we must examine our knowledge of universals. This
consideration will occupy us in the following chapter, where we shall
find that it solves the problem of _a priori_ knowledge, from which we
were first led to consider universals.

CHAPTER X. ON OUR KNOWLEDGE OF UNIVERSALS

In regard to one man's knowledge at a given time, universals, like
particulars, may be divided into those known by acquaintance, those
known only by description, and those not known either by acquaintance or
by description.

Let us consider first the knowledge of universals by acquaintance. It is
obvious, to begin with, that we are acquainted with such universals as
white, red, black, sweet, sour, loud, hard, etc., i.e. with qualities
which are exemplified in sense-data. When we see a white patch, we are
acquainted, in the first instance, with the particular patch; but by
seeing many white patches, we easily learn to abstract the whiteness
which they all have in common, and in learning to do this we are
learning to be acquainted with whiteness. A similar process will make us
acquainted with any other universal of the same sort. Universals of this
sort may be called 'sensible qualities'. They can be apprehended with
less effort of abstraction than any others, and they seem less removed
from particulars than other universals are.

We come next to relations. The easiest relations to apprehend are those
which hold between