BODY AND PRACTICE IN KANT

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As to the way in which each part of an object is placed with respect to
our body, we perceive it no differently through our eyes than with our
hands. Moreover, our knowledge of it does not depend on an image
or on any action by the object, but only on the arrangement of the
small parts of the brain where the nerves originate – for this
arrangement, which changes so little with each shift in disposition of
the members reached by the nerves, is of such a nature as not only to
make known to the soul where each part of the body it animates is in
relation to the other parts but also to enable the soul to shift its
attention to the entire area that lies within such straight lines as we
might imagine drawn from the end of each of these parts and
extended to infinity. 11
Descartes also draws special attention to the movements of our muscles:
Likewise, when our eye or our head is turned toward one side, our
soul is alerted by the change that the nerves leading from the muscles
used for these movements cause in our brain. 12
In a parallel argument, in his Essay towards a new theory of vision
Berkeley draws attention to the sensations aroused by the movements of
the pupils as one of the many sensations from which we gain information
on the spatial distance between objects and ourselves.
It is certain by Experience, that when we look at a near Object with
both Eyes, according as it approaches, or recedes from us, we alter
the Disposition of our Eyes, by lessening or widening the Interval
between the Pupils. This Disposition or Turn of the Eyes is attended
with a Sensation, which seems to me, to be that which in this Case
brings the Idea of greater, or lesser Distance into the Mind. 13
The idea of spatial properties of objects in the first place, however,
according to Berkeley, is produced by touch. The idea that objects do not
change in size, contrary to what seems to be the fact from our visual
impressions of them as we either approach or recedes from them, is also
derived from touch, he argues:
11 Quoted from Herrnstein (1986), 113-14.
12 Ibid., 114.
13 Ibid., 120.
BODY AND SPACE