mistake. If the ignorant observer were unable to do that, he might
remain permanently under the impression that the main lines were out of
parallelism. And all the infirmities of eye and ear, touch and taste,
are discovered and checked by the fact that the erroneous impressions
presently strike against fact and discover an incompatibility with it.
If they did not we should never have discovered them. If on the other
hand they are so incompatible with fact as to endanger the lives of the
beings labouring under such infirmities, they would tend to be
eliminated from among our defects.

The presumption to which biological science brings one is that the
senses and mind will work as well as the survival of the species may
require, but that they will not work so very much better. There is no
ground in matter-of-fact experience for assuming that there is any more
inevitable certitude about purely intellectual operations than there is
about sensory perceptions. The mind of a man may be primarily only a
food-seeking, danger-avoiding, mate-finding instrument, just as the mind
of a dog is, just as the nose of a dog is, or the snout of a pig.

You see the strong preparatory reason there is in this view of life for
entertaining the suppositions that:--

The senses seem surer than they are.

The thinking mind seems clearer than it is and is more positive than it
ought to be.

The world of fact is not what it appears to be.