e, and
precipitated together as the stable part of the whole experience--chaos,
under the name of the physical world."*

* "Essays in Radical Empiricism," pp. 32-3.

In this passage James speaks, by mere inadvertence, as though the
phenomena which he is describing as "mental" had NO effects. This is, of
course, not the case: they have their effects, just as much as physical
phenomena do, but their effects follow different laws. For example,
dreams, as Freud has shown, are just as much subject to laws as are the
motions of the planets. But the laws are different: in a dream you may
be transported from one place to another in a moment, or one person
may turn into another under your eyes. Such differences compel you to
distinguish the world of dreams from the physical world.

If the two sorts of causal laws could be sharply distinguished, we could
call an occurrence "physical" when it obeys causal laws appropriate to
the physical world, and "mental" when it obeys causal laws appropriate
to the mental world. Since the mental world and the physical world
interact, there would be a boundary between the two: there would be
events which would have physical causes and mental effects, while there
would be others which would have mental causes and physical effects.
Those that have physical causes and mental effects we should define as
"sensations." Those that have mental causes and physical effects might
perhaps be identified with what we call voluntary movements; but they do
not concern us at present.

These definitions would have all the precision that could be desired if
the distinction between physical and psychological causation were clear
and sharp. As a matter of fact, however, this distinction is, as yet, by
no means sharp. It is possible that, with fuller knowledge, it will be
found to be no more ultimate than the distinction between the laws of
gases and the laws of rigid bodies. It also suffers from the fact that
an event may be an effect of several causes according to several causal
laws we cannot, in general, point to anything unique as THE cause of
such-and-such an event. And finally it is by no means certain that
the peculiar causal laws which govern mental events are not really
physiological. The law of habit, which is one of the most distinctive,
may be fully explicable in terms of the peculiarities of nervous tissue,
and these peculiarities, in turn, may be explicable by the laws of
physics. It seems, th