es, this would be a violation of
the law of the constancy of the sum of energy. For in this case there
would occur, at a certain point in the nexus of phenomena, a piece of work
done, however small it might be, for which there was no equivalent of
energy in the previous constitution. But this is, since the days of
Helmholtz, an impossible assumption. And thus all those experiments and
theories on what we have called the "second line" of mechanistic
interpretation of the universe show themselves to be relevant to our
present subject.

Interpretations of the psychical such as these have given rise to four
peculiar "isms" of an epistemological nature, _i.e._, related to a theory
of knowledge. Not infrequently they are the historical antecedents which
result in the naturalistic theory of the psychical. These are nominalism
and sensualism, empiricism and a-posteriorism, which, setting themselves
against epistemological rationalism, assail the dignity, the independence,
and the autonomy of the thinking mind. They are so necessarily and closely
associated with naturalism that their fate is intimately bound up with its
fate, and they are corroborated or refuted with it. And it would be
possible to conduct the whole discussion with which we are concerned
purely with reference to these four "isms." The strife really begins in
their camp.

The soul is a _tabula rasa_, all four maintain, a white paper on which, to
begin with, nothing is inscribed. It brings with it neither innate
knowledge nor commands. What it possesses in the way of percepts,
concepts, opinions, convictions, principles of action, rules of conduct,
are inscribed upon it through experience (empiricism). That is, not
antecedent to, but subsequent to experience (a posteriori). But experience
can only be gained through the senses. Only thus does reality penetrate
into and stamp itself upon us. "What was not first in the senses (sensus)
cannot be in the intelligence." What the senses convey to us alone builds
up our mental content, from mere sensory perceptions upwards to the most
abstract ideas from the simplest psychical elements up to the most complex
ideas, concepts, and conclusions, to the most varied imaginative
constructions. And in the development of the mental content the "soul"
itself is merely the stage upon which all that is acquired through the
senses crowds, and jostles, and unites to form images, perceptions, and
precepts. But it is itself purely passiv