t is sufficiently
accurate for the purpose of these lectures, the scope of which is not
philosophical but historical.

[Sidenote: Two kinds of experience, the experience of our own mind and
the experience of an external world.]

Now experience in the widest sense of the word may be conveniently
distinguished into two sorts, the experience of our own mind and the
experience of an external world. The distinction is indeed, like the
others with which I am dealing at present, rather practically useful
than theoretically sound; certainly it would not be granted by all
philosophers, for many of them have held that we neither have nor with
our present faculties can possibly attain to any immediate knowledge or
perception of an external world, we merely infer its existence from our
own sensations, which are as strictly a part of our mind as the ideas
and emotions of our waking life or the visions of sleep. According to
them, the existence of matter or of an external world is, so far as we
are concerned, merely an hypothesis devised to explain the order of our
sensations; it never has been perceived by any man, woman, or child who
ever lived on earth; we have and can have no immediate knowledge or
perception of anything but the states and operations of our own mind. On
this theory what we call the world, with all its supposed infinitudes of
space and time, its systems of suns and planets, its seemingly endless
forms of inorganic matter and organic life, shrivels up, on a close
inspection, into a fleeting, a momentary figment of thought. It is like
one of those glass baubles, iridescent with a thousand varied and
delicate hues, which a single touch suffices to shatter into dust. The
philosopher, like the sorcerer, has but to wave his magic wand,

"And, like the baseless fabric of this vision,
The cloud-capped towers, the gorgeous palaces,
The solemn temples, the great globe itself,
Yea, all which it inherit, shall dissolve
And, like this insubstantial pageant faded,
Leave not a rack behind. We are such stuff
As dreams are made on, and our little life
Is rounded with a sleep."

[Sidenote: The distinction rather popular and convenient than
philosophically strict.]

It would be beyond my province, even if it were within my power, to
discuss these airy speculations, and thereby to descend into the arena
where for ages subtle dialecticians have battled with each other over
the reality or unreality of an externa