ments
is equivalent to imperfect co-ordination of their physical, that is to
say, nervous, conditions, imperfect in the evolutionist's sense, as not
exactly according with external relations. So far as illusions of
suggestion (passive illusions) are concerned, the error is connected
with organized tendencies, due to a limited action of experience. On the
other hand, illusions of preconception (active illusions) usually
involve no such deeply fixed or permanent organic connections, but
merely a temporary confluence of nerve-processes.[149] The nature of the
physical process is best studied in the case of errors of
sense-perception. Yet we may hypothetically argue that even in the case
of the most complex errors, as those of memory and of belief, there is
implied a deviation in the mode of connection of nervous structures
(whether the connection be permanent or temporary) from the external
order of facts.

And now we are in a position to see whether illusion is ultimately
distinguishable from other modes of error, namely, those incident to
conscious processes of reasoning. It must have been plain to an
attentive reader throughout our exposition that, in spite of our
provisional distinction, no sharp line can be drawn between much of
what, on the surface, looks like immediate knowledge, and consciously
derived or inferred knowledge. On its objective side, reasoning may be
roughly defined as a conscious transition of mind from certain facts or
relations of facts to other facts or relations recognized as similar.
According to this definition, a fallacy would be a hasty, unwarranted
transition to new cases not identical with the old. And a good part of
immediate knowledge is fundamentally the same, only that here, through
the exceptional force of association and habit, the transition is too
rapid to be consciously recognized. Consequently, illusion becomes
identified at bottom with fallacious inference: it may be briefly
described as collapsed inference. Thus, illusory perception and
expectation are plainly a hasty transition of mind from old to new, from
past to present, conjunctions of experience.[150] And, as we have seen,
an illusory general belief owes its existence to a coalescence of
representations of known facts or connections with products of
imagination which simulate the appearance of inferences from these
facts.

In the case of memory, in so far as it is not aided by reasoning from
present signs, there seems t