is not referred to any other
thing. It seemed to follow that there could be only one substance.

Spinoza modified Descartes' doctrine in that he refused to regard mind
and matter as substances at all. He made them unequivocally attributes
of the one and only substance, which he called God.

The thought which influenced Spinoza had impressed many minds before
his time, and it has influenced many since. One need not follow him in
naming the unitary something to which mind and matter are referred
substance. One may call it Being, or Reality, or the Unknowable, or
Energy, or the Absolute, or, perhaps, still something else. The
doctrine has taken many forms, but he who reads with discrimination
will see that the various forms have much in common.

They agree in maintaining that matter and mind, as they are revealed in
our experience, are not to be regarded as, in the last analysis, two
distinct kinds of thing. They are, rather, modes or manifestations of
one and the same thing, and this is not to be confounded with either.

Those who incline to this doctrine take issue with the materialist, who
assimilates mental phenomena to physical; and they oppose the idealist,
who assimilates physical phenomena to mental, and calls material things
"ideas." We have no right, they argue, to call that of which ideas and
things are manifestations either mind or matter. It is to be
distinguished from both.

To this doctrine the title of _Monism_ is often appropriated. In this
chapter I have used the term in a broader sense, for both the
materialist and the spiritualist maintain that there is in the universe
but one kind of thing. Nevertheless, when we hear a man called a
monist without qualification, we may, perhaps, be justified in
assuming, in the absence of further information, that he holds to some
one of the forms of doctrine indicated above. There may be no logical
justification for thus narrowing the use of the term, but logical
justification goes for little in such matters.

Various considerations have moved men to become monists in this sense
of the word. Some have been influenced by the assumption--one which
men felt impelled to make early in the history of speculative
thought--that the whole universe must be the expression of some unitary
principle. A rather different argument is well illustrated in the
writings of Professor Hoeffding, a learned and acute writer of our own
time. It has influenced so many that