nly the causal
differences which are undeniable. Without condemning the intrinsic
theory, we can define discomfort and pleasure as consisting in causal
properties, and say only what will hold on either of the two theories.
Following this course, we shall say:

"Discomfort" is a property of a sensation or other mental occurrence,
consisting in the fact that the occurrence in question stimulates
voluntary or reflex movements tending to produce some more or less
definite change involving the cessation of the occurrence.

"Pleasure" is a property of a sensation or other mental occurrence,
consisting in the fact that the occurrence in question either does not
stimulate any voluntary or reflex movement, or, if it does, stimulates
only such as tend to prolong the occurrence in question.*

* Cf. Thorndike, op. cit., p. 243.

"Conscious" desire, which we have now to consider, consists of desire
in the sense hitherto discussed, together with a true belief as to its
"purpose," i.e. as to the state of affairs that will bring quiescence
with cessation of the discomfort. If our theory of desire is correct,
a belief as to its purpose may very well be erroneous, since only
experience can show what causes a discomfort to cease. When the
experience needed is common and simple, as in the case of hunger, a
mistake is not very probable. But in other cases--e.g. erotic desire in
those who have had little or no experience of its satisfaction--mistakes
are to be expected, and do in fact very often occur. The practice of
inhibiting impulses, which is to a great extent necessary to civilized
life, makes mistakes easier, by preventing experience of the actions to
which a desire would otherwise lead, and by often causing the inhibited
impulses themselves to be unnoticed or quickly forgotten. The perfectly
natural mistakes which thus arise constitute a large proportion of what
is, mistakenly in part, called self-deception, and attributed by Freud
to the "censor."

But there is a further point which needs emphasizing, namely, that a
belief that something is desired has often a tendency to cause the very
desire that is believed in. It is this fact that makes the effect of
"consciousness" on desire so complicated.

When we believe that we desire a certain state of affairs, that often
tends to cause a real desire for it. This is due partly to the influence
of words upon our emotions, in rhetoric for example, and partly to the
general fact t