analogies, now, the movement of the eye from _O_ to _P_, that is, the
arc which I traverse, must be underestimated" (_ibid._, S. 67). There
is thus a discrepancy between our two estimates of the distance _OP_.
This discrepancy is felt during the movement, and can be harmonized
only if we seem to see the two fixation-points move apart, until the
arc between them, in terms of innervation-feeling, feels equal to the
distance _OP_ in terms of its visual subdivisions. Now either _O_ and
_P_ can both seem to move apart from each other, or else one can seem
fixed while the other moves. But the eye has for its goal _P_, which
ought therefore to have a definite position. "_P_ appears fixed
because, as goal, I hold it fast in my thought" (_loc. citat._). It
must be _O_, therefore, which appears to move; that is, _O_ must dart
backward as the eye moves forward toward _P_. Thus Lipps explains the
illusion.

[10] Lipps, Th., _Zeitschrift f. Psychologie u. Physiologie der
Sinnesorgane_, 1890, I., S. 60-74.

Such an explanation involves many doubtful presuppositions, but if we
were to grant to Lipps those, the following consideration would
invalidate his account. Whether the feeling of innervation which he
speaks of as being the underestimated factor is supposed to be a true
innervation-feeling in the narrower sense, or a muscular sensation
remembered from past movements, it would in the course of experience
certainly come to be so closely associated with the corresponding
objective distance as not to feel less than this. So far as an
innervation-feeling might allow us to estimate distance, it could have
no other meaning than to represent just that distance through which
the innervation will move the organ in question. If _OP_ is a distance
and _i_ is the feeling of such an innervation as will move the eye