38 THEORETICAL BIOLOGY 



bay from the heights of Posilippo, seems very far off and not 

 remarkably high. If, on the other hand, one turns into a 

 street that leads towards Vesuvius, the mountain is suddenly 

 quite close at hand and of gigantic size. 



We get a most disconcerting effect of this kind if from 

 Monte Pincio we turn our eyes towards St Peter's, far away 

 across the great expanse of Rome with all its countless streets, 

 palaces, piazzas and bridges. Then the great church appears 

 to rise in the far distance not so very high above the Eternal 

 City. But if we step back about fifteen metres from the 

 balustrade, so that, for our eyes focussed on the distance, 

 it is brought into sharp relief and at the same time covers 

 the town, then almost immediately behind it the magnificent 

 building rises up in overwhelming size. At the same time 

 the horizon also seems to come nearer. 



Now, in all these cases, it is not the retinal image of the 

 object that has become larger ; it has actually become 

 smaller : and yet, in spite of that, the object appears to us 

 nearer and larger. Nor has it moved away from the horizon ; 

 the horizon has approached us along with it. What has 

 happened is that the object has moved away from the extended 

 and objectless, towards which it now stands in a new relation. 



Since it is without objects, the extended possesses no sort 

 of feature by which we can measure its magnitude or divide 

 it up into parts. It has the effect always of an indivisible 

 whole, to which different objects stand in different relations. 

 The observer, however, is always at the same distance from 

 the extended. If the objects change their distance from the 

 observer, then, according to the number of distance-signs they 

 present, their relation to the extended simultaneously changes. 



The extended has no definite order of magnitude, but is 

 in itself magnitude. Everything that approaches it, or seems 

 to approach it, must consequently get smaller and smaller. 



When we look at it in this way, we begin to understand 



