186 PSYCHOLOGY. 



througli these constant changes every field of seen things 

 comes at last to be thought of as always having a fringe 

 of other things possible to be seen spreading in all directions 

 round about it. Meanwhile the movements concomitantly 

 with which the various fields alternate are also felt and re- 

 membered ; and gradually (through association) this and 

 that movement come in our thought to suggest this or that 

 extent of fresh objects introduced. Gradually, too, since 

 the objects vary indefinitely in kind, we abstract from 

 their several natures and think separately of their mere 

 extents, of which extents the various movements remain as 

 the only constant introducers and associates. More and 

 more, therefore, do we think of movement and seen extent 

 as mutually involving each other, until at last (with Bain 

 and J. S. Mill) we may get to regard them as synonymous, 

 and say, " What is the meaning of the ivord extent, unless it 

 be possible movement?"* We forget in this conclusion 

 that (whatever intrinsic extensiveness the movements may 

 appear endowed with), that seen spreadoutness which is 

 the pattern of the abstract extensiveness which we imagine 

 came to us. originally from the retinal sensation. 



The muscular sensations of the eyeball signify this sort 

 of visible spreadoutness, just as this visible spreadoutness 

 may come in later experience to signify the ' real ' bulks, 

 distances, lengths and breadths known to touch and loco- 

 motion, f To the very end, however, in us seeing men, 

 the quality, the nature, the sort of thing roe mean by exten- 

 siveness, would seem to be the sort of feeling which our re- 

 tinal stimulations bring. 



In one deprived of sight the principles by which the 

 notion of real space is constructed are the same. Skin- 

 feelings take in him the place of retinal feelings in giving 



* See, e.g., Bain's Senses and Intellect, pp. 366-7, 371. 



f When, for example, a baby looks at its own moving hand, it sees 

 one object at the same time that it feels another. Both interest its 

 attention, and it locates them together. But the felt object's size is the 

 more constant size, just as the felt object is, on the whole, the more in- 

 teresting and important object ; and so the retinal sensations become re- 

 garded as its signs and have their ' real space- values ' interpreted in 

 tangible terms. 



