tuting one
continuous process.

There are different ways in which this independent activity of the
imagination may falsify our perceptions. Thus, we may voluntarily choose
to entertain a certain image for the moment, and to look at the
impression in a particular way, and within certain limits such
capricious selection of an interpretation is effectual in giving a
special significance to an impression. Or the process of independent
preperception may go on apart from our volitions, and perhaps in spite
of these, in which case the illusion has something of the irresistible
necessity of a passive illusion. Let us consider separately each mode
of production.

_Voluntary Selection of Interpretation._

The action of a capricious exercise of the imagination in relation to an
impression is illustrated in those cases where experience and suggestion
offer to the interpreting mind an uncertain sound, that is to say, where
the present sense-signs are ambiguous. Here we obviously have a choice
of interpretation. And it is found that, in these cases, what we see
depends very much on what we wish to see. The interpretation adopted is
still, in a sense, the result of suggestion, but of one particular
suggestion which the fancy of the moment determines. Or, to put it
another way, the caprice of the moment causes the attention to focus
itself in a particular manner, to direct itself specially to certain
aspects and relations of objects.

The eye's interpretation of movement, already referred to, obviously
offers a wide field for this play of selective imagination. When looking
out of the window of a railway carriage, I can at will picture to my
mind the trees and telegraph posts as moving objects. Sometimes the true
interpretation is so uncertain that the least inclination to view the
phenomenon in one way determines the result. This is illustrated in a
curious observation of Sinsteden. One evening, on approaching a windmill
obliquely from one side, which under these circumstances he saw only as
a dark silhouette against a bright sky, he noticed that the sails
appeared to go, now in one direction, now in another, according as he
imagined himself looking at the front or at the back of the
windmill.[48]

In the interpretation of geometrical drawings, as those of crystals,
there is, as I have observed, a general tendency to view the flat
delineation as answering to a raised object, or a body in relief,
according to the common run of