ily
immediate in the sense in which purely presentative knowledge is so,
since it can be shown to follow from something else. So a general
proposition, though through familiarity and innumerable illustrations it
has acquired a self-evident character, is seen with a very little
inspection to be less fundamentally and essentially so than the
proposition, "I am now feeling pain;" and it will be found that even
with respect to memory, when the remembered event is at all remote, the
process of cognition approximates to a mediate operation, namely, one of
inference. What the relative values of these different kinds of
immediate knowledge are is a point which will have to be touched on at
the end of our study. Here it must suffice to warn the reader against
the supposition that this value is assumed to be identical.
It might seem at a first glance to follow from this four-fold scheme of
immediate or quasi-immediate knowledge that there are four varieties of
illusion. And this is true in the sense that these four heads cover all
the main varieties of illusion. If there are only four varieties of
knowledge which can lay any claim to be considered immediate, it must be
that every illusion will simulate the form of one of these varieties,
and so be referable to the corresponding division.
But though there are conceivably these four species of illusion, it does
not follow that there are any actual instances of each class
forthcoming. This we cannot determine till we have investigated the
nature and origin of illusory error. For example, it might be found that
introspection, or the immediate inspection of our own feelings or mental
states, does not supply the conditions necessary to the production of
such error. And, indeed, it is probable that most persons, antecedently
to inquiry, would be disposed to say that to fall into error in the
observation of what is actually going on in our own minds is
impossible.
With the exception of this first division, however, this scheme may
easily be seen to answer to actual phenomena. That there are illusions
of perception is obvious, since it is to the errors of sense that the
term illusion has most frequently been confined. It is hardly less
evident that there are illusions of memory. The peculiar difficulty of
distinguishing between a past real event and a mere phantom of the
imagination, illustrated in the exclamation, "I either saw it or dreamt
it," sufficiently shows that memory is li
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