It does not mean, of course, that he has only two kinds of experiences.
The phenomena which are revealed to us are indefinitely varied; all
physical phenomena are not just alike, and all mental phenomena are not
just alike.

Nevertheless, amid all the bewildering variety that forces itself upon
our attention, there stands out one broad distinction, that of the
physical and the mental. It is a distinction that the man who has done
no reading in the philosophers is scarcely tempted to obliterate; to
him the world consists of two kinds of things widely different from
each other; minds are not material things and material things are not
minds. We are justified in regarding this as the opinion of the plain
man even when we recognize that, in his endeavor to make clear to
himself what he means by minds, he sometimes speaks as though he were
talking about something material or semi-material.

Now, the materialist allows these two classes to run together; so does
the idealist. The one says that everything is matter; the other, that
everything is mind. It would be foolish to maintain that nothing can
be said for either doctrine, for men of ability have embraced each.
But one may at least say that both seem to be refuted by our common
experience of the world, an experience which, so far as it is permitted
to testify at all, lifts up its voice in favor of _Dualism_.

Dualism is sometimes defined as the doctrine that there are in the
world two kinds of substances, matter and mind, which are different in
kind and should be kept distinct. There are dualists who prefer to
avoid the use of the word substance, and to say that the world of our
experiences consists of physical phenomena and of mental phenomena, and
that these two classes of facts should be kept separate.

The dualist may maintain that we have a direct knowledge of matter and
of mind, and he may content himself with such a statement, doing little
to make clear what we mean by matter and by mind. In this case, his
position is little different from that of the plain man who does not
attempt to philosophize. Thomas Reid (section 50) belongs to this
class.

On the other hand, the dualist may attempt to make clear, through
philosophical reflection, what we mean by the matter and mind which
experience seems to give us. He may conclude:--

(1) That he must hold, as did Sir William Hamilton, that we perceive
directly only physical and mental phenomena, but are just