ch cases, though
there is some real thing corresponding to the perception, this is seen
in a highly defective, distorted, and misleading form. In like manner,
we can say that the images of memory often get obscured, distorted, and
otherwise altered when they have receded into the dim distance, and are
looked back upon through a long space of intervening mental experience.
Finally, class (3) has its visual counterpart in erroneous perceptions
of distance, as when, for example, owing to the clearness of the
mountain atmosphere and the absence of intervening objects, the side of
the Jungfrau looks to the inexperienced tourist at Wengernalp hardly
further than a stone's throw. It will be found that when our memory
falsifies the date of an event, the error arises much in the same way as
a visual miscalculation of distance.

This threefold division of illusions of memory is plainly a rather
superficial one, and not based on distinctions of psychological nature
or origin. In order to make our treatment of the subject scientific as
well as popular, it will be necessary to introduce the distinction
between the passive and the active factor under each head. It will be
found, I think, without forcing the analogy too far, that here, as in
the case of the illusions of perception and introspection, error is
attributable now to misleading suggestion on the part of the mental
content of the moment, now to a process of incorporating into this
content a mental image not suggested by it, but existing independently.

If we are to proceed as we did in the case of the illusions of sense,
and take up the lower stages of error first of all, we shall need to
begin with the third class of errors, those of localization in time, or
of what may be called mnemonic perspective. It has been already observed
that the definite localization of a mnemonic image is only an occasional
accompaniment of what is loosely called recollection. Hence, error as
to the position of an event in the past chain of events would seem to
involve the least degree of violation of the confidence which we are
wont to repose in memory. After this, we may proceed to the discussion
of the second class, which I may call distortions of the mnemonic
picture. And, finally, we may deal with the most signal and palpable
variety of error of memory, namely, the illusions which I have called
mnemonic spectra.

_Illusions of Perspective: A. Definite Localization._

In order to unders