which we actually find ourselves; not a
hypothetical, inferred, unperceived world, but the world of the things
we actually perceive. He distinguished carefully between what is real
and what is merely imaginary, though he called both "ideas"; and he
recognized something like a system of nature. And, by the argument
from analogy which we have already examined (section 41), he inferred
the existence of other finite minds and of a Divine Mind.

But just as John Locke had not completely thought out the consequences
which might be deduced from his own doctrines, so Berkeley left, in his
turn, an opening for a successor. It was possible for that acutest of
analysts, David Hume (1711-1776), to treat him somewhat as he had
treated Locke.

Among the objects of human knowledge Berkeley had included the _self_
that perceives things. He never succeeded in making at all clear what
he meant by this object; but he regarded it as a substance, and
believed it to be a cause of changes in ideas, and quite different in
its nature from all the ideas attributed to it. But Hume maintained
that when he tried to get a good look at this self, to catch it, so to
speak, and to hold it up to inspection, he could not find anything
whatever save perceptions, memories, and other things of that kind.
The self is, he said, "but a bundle or collection of different
perceptions which succeed each other with inconceivable rapidity, and
are in a perpetual flux and movement."

As for the objects of sense, our own bodies, the chairs upon which we
sit, the tables at which we write, and all the rest--these, argues
Hume, we are impelled by nature to think of as existing continuously,
but we have no evidence whatever to prove that they do thus exist. Are
not the objects of sense, after all, only sensations or impressions?
Do we not experience these sensations or impressions interruptedly?
Who sees or feels a table continuously day after day? If the table is
but a name for the experiences in question, if we have no right to
infer material things behind and distinct from such experiences, are we
not forced to conclude that the existence of the things that we see and
feel is an interrupted one?

Hume certainly succeeded in raising more questions than he succeeded in
answering. We are compelled to admire the wonderful clearness and
simplicity of his style, and the acuteness of his intellect, in every
chapter. But we cannot help feeling that he does injust