44 THEORETICAL BIOLOGY 



In doing this, my normal vision was restored — the sort 

 of vision that corresponds to a movement of touch by the 

 hand as it comes against objects, now close by, now further 

 away ; as it does so, the direction-signs orientate us as to 

 the position of the obstacles in space. With our glance, as 

 with our hand, we come up against more and more remote 

 obstructions until we get to the horizon, behind which lies the 

 extended, offering no resistance. 



In our visual space every coloured surface, of whatever 

 kind it may be, constitutes a check, lying either close at hand 

 or far away. All arouse the same sensation, namely that of 

 an obstacle, like the resistances which present themselves to 

 the groping hand. In virtue of this, they get the character of 

 material things, which, taken generally, mean nothing but 

 actual obstructions. 



And so it comes about that we describe as substances all 

 things that prove their reality as obstacles. Without pre- 

 judice to this common property of all forms of matter, the 

 various substances can evoke the most manifold qualities of 

 the senses of sight and touch. And since we project all the 

 other sense-qualities as well, and comprehend all their effects 

 as coming to us from the outside, we connect these likewise 

 with the forms of matter in space, as the only realities known 

 to us outside those residing in our own subject. 

 \ The content of the space surrounding us consists of motion 



and resistance. The localising of the various resistances is 

 necessary for the movement of our own body in space. It 

 is much more important than an awareness of objects. For 

 each rapid movement we must have accurate information as 

 to the place where a resistance lies, if we are not to injure 

 ourselves ; and we will avoid an apparent obstacle rather 

 than come up against a real one. 



We are not yet ready to discuss accurate conception of 

 form, for that pertains to the construction of objects. All 



