The
follower of Berkeley or Newton has satisfied himself in the negative.

But the case is very different in my intercourse with my fellow-men.
Agreeably to the statement already made I know the reality of human
nature; for I feel the particulars that constitute it within myself.
The impressions I receive from that intercourse say something to me;
for they talk to me of beings like myself. My own existence becomes
multiplied in infinitum. Of the possibility of matter I know nothing;
but with the possibility of mind I am acquainted; for I am myself an
example. I am amazed at the consistency and systematic succession of the
phenomena of the material universe; though I cannot penetrate the veil
which presents itself to my grosser sense, nor see effects in their
causes. But I can see, in other words, I have the most cogent reasons
to believe in, the causes of the phenomena that occur in my apparent
intercourse with my fellow-men. What solution so natural, as that
they are produced by beings like myself, the duplicates, with certain
variations, of what I feel within me?

The belief in the reality of matter explains nothing. Supposing it to
exist, if Newton is right, no particle of extraneous matter ever touched
the matter of my body; and therefore it is not just to regard it as
the cause of my sensations. It would amount to no more than two systems
going on at the same time by a preestablished harmony, but totally
independent of and disjointed from each other.

But the belief in the existence of our fellow-men explains much. It
makes level before us the wonder of the method of their proceedings, and
affords an obvious reason why they should be in so many respects like
our own. If I dismiss from my creed the existence of inert matter, I
lose nothing. The phenomena, the train of antecedents and consequents,
remain as before; and this is all that I am truly concerned with. But
take away the existence of my fellow-men; and you reduce all that is,
and all that I experience, to a senseless mummery. "You take my life,
taking the thing whereon I live."

Human nature, and the nature of mind, are to us a theme of endless
investigation. "The proper study of mankind is man." All the subtlety
of metaphysics, or (if there be men captious and prejudiced enough
to dislike that term) the science of ourselves, depends upon it. The
science of morals hangs upon the actions of men, and the effects they
produce upon our brother-men, in a nar