dergo within the surrounding _totality of
space_, which we conceive of as fixed. We estimate according to the
length of such movements, or at least we deduce therefrom, the
distance through fixed space which our view by virtue of these
movements has traversed.... They themselves are nothing for our
consciousness but a series of purely intensive states. But in
experience they can come to _indicate_ distance traversed." Now in
turning the eye from a luminous object, _O_, to some other
fixation-point, _P_, the distance as simply contemplated is more or
less subdivided or filled in by the objects which are seen to lie
between _O_ and _P_, or if no such objects are visible the distance is
still felt to consist of an infinity of points; whereas the muscular
innervation which is to carry the eye over this very distance is an
undivided unit. But it is this which gives us our estimate of the arc
we move through, and being thus uninterrupted it will appear shorter
than the contemplated, much subdivided distance _OP_, just as a
continuous line appears shorter than a broken line. "After such
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
remembere