ach of
us, so to speak, the three great divisions of sound, base, tenor and
treble. We have each the same number of keys, capable of being struck,
consecutively or with alternations, at the will of the master. We can
utter the same sound or series of sounds, or sounds of a different
character, but which respond to each other. My neighbour therefore being
of the same nature as myself, what passes within me may be regarded as
amounting to a commanding evidence that he is a real being, having a
proper and independent existence.

There is further something still more impressive and irresistible in the
notices I receive respecting the minds of other men. The sceptics whose
reasonings I am here taking into consideration, admit, each man for
himself, the reality of his own existence. There is such a thing
therefore as human nature; for he is a specimen of it. Now the idea of
human nature, or of man, is a very complex thing. He is in the first
place the subject of sensible impressions, however these impressions are
communicated to him. He has the faculties of thinking and feeling. He is
subject to the law of the association of ideas, or, in other words, any
one idea existing in his mind has a tendency to call up the ideas of
other things which have been connected with it in his first experience.
He has, be it delusive or otherwise, the sense of liberty of action.

But we will go still further into detail as to the nature of man.

Our lives are carried forward by the intervention of what we call meat,
drink and sleep. We are liable to the accidents of health and sickness.
We are alternately the recipients of joy and sorrow, of cheerfulness and
melancholy. Our passions are excited by similar means, whether of love
or hatred, complacency or indignation, sympathy or resentment. I could
fill many pages with a description of the properties or accidents, which
belong to man as such, or to which he is liable.

Now with all these each man is acquainted in the sphere of his inward
experience, whether he is a single being standing by himself, or is an
individual belonging to a numerous species.

Observe then the difference between my acquaintance with the phenomena
of the material universe, and with the individuals of my own species.
The former say nothing to me; they are a series of events and no more;
I cannot penetrate into their causes; that which gives rise to my
sensations, may or may not be similar to the sensations themselves.