without special experience of human bodies you could not know how or when their appearance indicates vitality or character; without experience of animals you could not know that the drawing of the bull hunt indicates activity, courage, ferocity. You cannot read these things off from the patterns or the colour-combinations; you have ultimately to arrive at them from the knowledge of facts. When you come to human portraiture, the reading of the human countenance, geometrical properties of lines and shapes help you not at all, or hardly at all. You have to rely upon special lessons, learned in the school of life.
This is, I think, the difficulty as it presents itself. I have purposely overstated it a little.
The first thing that strikes us is that it is extraordinarily parallel to the difficulty as to how far necessary knowledge can be had in the sphere of natural science. You cannot see the chemical properties of substances in them, as you can see the properties of circles or triangles; you
