mount of actual impression becomes evanescent. When
this point is reached, the act of imagination shows itself as a purely
creative process, or an hallucination.

While we may thus trace the progress of illusion towards hallucination
by means of the gradual increase in force and extent of the imaginative,
or indirect, as opposed to the sensuous, or direct, element in
perception, we have found a second starting-point for this movement in
the mechanism of sensation, involving, as it does, the occasional
production of "subjective sensations." Such sensations constitute a
border-land between the regions of illusion in the narrow sense, and
hallucination. In their simplest and least developed form they may be
regarded, at least in the case of hearing and sight, as partly
hallucinatory; and they serve as a natural basis for the construction of
complete hallucinations, or hallucinatory percepts.

In these different ways, then, the slight, scarcely noticeable illusions
of normal life lead up to the most startling hallucinations of abnormal
life. From the two poles of the higher centres of attention and
imagination on the one side, and the lower regions of nervous action
involved in sensation on the other side, issue forces which may, under
certain circumstances, develop into full hallucinatory percepts. Thus
closely is healthy attached to morbid mental life. There seems to be no
sudden break between our most sober every-day recognitions of familiar
objects and the wildest hallucinations of the demented. As we pass from
the former to the latter, we find that there is never any abrupt
transition, never any addition of perfectly new elements, but only that
the old elements go on combining in ever new proportions.

The connection between the illusory side of our life and insanity may be
seen in another way. All illusion has as its negative condition an
interruption of the higher intellectual processes, the due control of
our mental representations by reflection and reason. In the case of
passive illusions, the error arises from our inability to subordinate
the suggestion made by some feature of the present impression to the
result of a fuller inspection of the object before us, or of a wider
reflection on the past. In other words, our minds are dominated by the
partial and the particular, to the exclusion of the total or the
general. In active illusions, again, the powers of judgment and
reflection, including those of calm percep