imary stuff of the world. It must be possible, if James is
right in his main contentions, that roughly the same stuff, differently
arranged, would not give rise to anything that could be called
"experience." This word has been dropped by the American realists, among
whom we may mention specially Professor R. B. Perry of Harvard and Mr.
Edwin B. Holt. The interests of this school are in general philosophy
and the philosophy of the sciences, rather than in psychology; they have
derived a strong impulsion from James, but have more interest than he
had in logic and mathematics and the abstract part of philosophy. They
speak of "neutral" entities as the stuff out of which both mind and
matter are constructed. Thus Holt says: "If the terms and propositions
of logic must be substantialized, they are all strictly of one
substance, for which perhaps the least dangerous name is neutral-stuff.
The relation of neutral-stuff to matter and mind we shall have presently
to consider at considerable length." *

* "The Concept of Consciousness" (Geo. Allen & Co., 1914),
p. 52.

My own belief--for which the reasons will appear in subsequent
lectures--is that James is right in rejecting consciousness as an
entity, and that the American realists are partly right, though not
wholly, in considering that both mind and matter are composed of a
neutral-stuff which, in isolation, is neither mental nor material. I
should admit this view as regards sensations: what is heard or seen
belongs equally to psychology and to physics. But I should say that
images belong only to the mental world, while those occurrences (if any)
which do not form part of any "experience" belong only to the physical
world. There are, it seems to me, prima facie different kinds of causal
laws, one belonging to physics and the other to psychology. The law
of gravitation, for example, is a physical law, while the law of
association is a psychological law. Sensations are subject to both kinds
of laws, and are therefore truly "neutral" in Holt's sense. But entities
subject only to physical laws, or only to psychological laws, are not
neutral, and may be called respectively purely material and purely
mental. Even those, however, which are purely mental will not have that
intrinsic reference to objects which Brentano assigns to them and which
constitutes the essence of "consciousness" as ordinarily understood. But
it is now time to pass on to other modern tendencies, also