Our survival depends so much on this sense of touch, that it is of the first importance to us. We must know whether the ground is hard enough for us to walk on, or whether there is a hole in front of us; and masses of colour rays striking the retina, which is what vision amounts to, will not of themselves tell us. ...
And likewise with hardness and softness, the child who strikes his head against the bed-post is forcibly reminded by nature that such things are to be avoided, and feeling that it is hard and that hardness has a certain look, it avoids that kind of thing in the future. And when it strikes its head against the pillow, it learns the nature of softness, and associating this sensation with the appearance of the pillow, knows in future that when softness is observed it need not be avoided as hardness must be.
Sight is therefore not a matter of the eye alone. A whole train of associations connected with the objective world is set going in the mind when rays of light strike the retina refracted from objects.
(from The Practice & Science of Drawing by Harold Speed)
Which statement best expresses the author's ideas regarding the sense of sight and the sense of touch?