the corresponding elements of conception, feeling and willing are
blended in each. We never turn away as instinctively from objectionable
colour arrangement as from an unpleasant smell. How small a part, on
the other hand, do the representations of odours play in our
recollection of past experiences, compared with those of sight.8 The
same is valid in descending measure for all other senses.

Of all senses, the sense of sight has in greatest measure the qualities
of a 'conceptual sense'. The experiences which it brings, and these
alone, were suitable as a basis for the new science, and even so a
further limitation was necessary. For in spite of the special quality
of the sense of sight, it is still not free from certain elements of
feeling and will - that is, from elements with the character of dream
or sleep. The first plays a part in our perception of colour; the
second, in observing the forms and perspective ordering of objects we
look at.

Here is repeated in a special way the threefold organization of man,
for the seeing of colour depends on an organic process apart from the
nerve processes and similar to that which takes place between heart and
lungs, whilst the seeing of forms and spatial vision depend upon
certain movements of the eyeball (quick traversing of the outline of
the viewed object with the line of sight, alteration of the angle
between the two axes of sight according to distance), in which the eye
is active as a sort of outer limb of the body, an activity which enters
our consciousness as little as does that of our limbs. It now becomes
clear that no world-content obtained in such more or less unconscious
ways could be made available for the building of a new scientific
world-conception. Only as much as man experiences through the sight of
a single, colour-blind eye, could be used.9