nd the foreign element imported
into it. An idea of memory seems sometimes to lose its proper moorings,
so to speak; to drift about helplessly among other ideas, and finally,
by some chance, to hook itself on to one of these, as though it
naturally belonged to it. Anybody who has had an opportunity of
carefully testing the truthfulness of his recollection of some remote
event in early life will have found how oddly extraneous elements become
incorporated into the memorial picture. Incidents get put into wrong
places, the wrong persons are introduced into a scene, and so on. Here
again we may illustrate the mnemonic illusion by a visual one. When a
tree standing before or behind a house and projecting above or to the
side of it is not sharply distinguished from the latter, it may serve to
give it a very odd appearance.

These confusions of the mental image may arise even when only a short
interval has elapsed. In the case of many of the fleeting impressions
that are only half recollected, this kind of error is very easy. Thus,
for example, I may have lent a book to a friend last week. I really
remember the act of lending it, but have forgotten the person. But I am
not aware of this. The picture of memory has unknowingly to myself been
filled up by this unconscious process of shifting and rearrangement, and
the idea of another person has by some odd accident got substituted for
that of the real borrower. If we could go deeply enough into the matter,
we should, of course, be able to explain why this particular confusion
arose. We might find, for example, that the two persons were associated
in my mind by a link of resemblance, or that I had dealings with the
other person about the same time. Similarly, when we manage to join an
event to a wrong place, we may find that it is because we heard of the
occurrence when staying at the particular locality, or in some other way
had the image of the place closely associated in our minds with the
event. But often we are wholly unable to explain the displacement.

So far I have been speaking of the passive processes by which the past
comes to wear a new face to our imaginations. In these our present
habits of feeling and thinking take no part; all is the work of the
past, of the decay of memory, and the gradual confusion of images. This
process of disorganization may be likened to the action of damp on some
old manuscript, obliterating some parts, altering the appearance of
others, a