484 POPULAR SCIENCE MONTHLY 



between the ideas of sight and touch, between the visible and tangible eye; for 

 certainly on the tangible eye nothing either is or seems to be painted. Again, 

 the visible eye, as well as all other visible objects, hath been shown to exist 

 only in the mind; which, perceiving its own ideas, and comparing them together, 

 does call some pictures in respect to others. What hath been said, being rightly 

 comprehended and laid together, does, I think, afford a full and genuine explana- 

 tion of the erect appearance of objects — which phenomenon, I must confess, I do 

 not see how it can be explained by any theories of vision hitherto made public. 

 In treating of these things, the use of language is apt to occasion some obscurity 

 and confusion, and create in us wrong ideas. For, language, being accommo- 

 dated to the common notions and prejudices of men, it is scarce possible to 

 deliver the naked and precise truth, without great circumlocution, impropriety, 

 and (to an unwary reader) seeming contradictions. 5 



That is to say, Berkeley insists upon the necessity for another and 

 more concrete analysis than that afforded by the resources of descrip- 

 tive language. 



Later, in " The Principles of Human Knowledge," Part I., he seems 

 to indicate that this profounder analysis must take a physiological 

 direction : 



The philosophic consideration of motion doth not imply the being of an 

 absolute Space, distinct from that which is perceived by sense, and related to 

 bodies. . . . When I excite a motion in some part of my body, if it be free or 

 without resistance, I say there is Space. But if I find a resistance, then I 

 say there is Body: and in proportion as the resistance to motion is lesser or 

 greater, I say the space is more or less pure. . . . When, therefore, supposing 

 all the world to be annihilated besides my own body, I say there still remains 

 pure Space; thereby nothing else is meant but only that I conceive it possible 

 for the limbs of my body to be moved on all sides without the least resistance : 

 but if that too were annihilated then there could be no motion, and consequently 

 no Space. 6 



Knowing little of physiology, Berkeley leaves the problem, stated 

 so far, indeed, but only stated. It is this : How can we derive space, 

 a general condition of external objects, from states of the body which, 

 in their very nature, differ utterly from this, their product? Twenty- 

 two years later, he returns to the question, and appears to raise it in 

 fresh form. In the Fourth Dialogue of " Alciphron, the Minute Phi- 

 losopher," he says : 



(Euphranor speaks:) "We perceive distance, not immediately, but by medi- 

 ation of a sign, which hath no likeness to it, or necessary connection with it, but 

 only suggests it from repeated experience, as words do things." (Alciphron 

 replies:) "Hold, Euphranor: now I think of it, the writers in optics tell us of 

 an angle made by the two optic axes, where they meet in the visible point or 

 object; which angle, the obtuser it is the nearer it shows the object to be, and 

 by how much the acuter, by so much the farther off; and this from a necessary 

 demonstrable connection." 7 



It is needless to add that Berkeley, although he makes physiological 

 reference and research inevitable, lived long before such a study of 

 " local signs " as that undertaken by Lotze was practicable. 



5 Sects. 119-20. "Sect. 116. 'Sect. S. 



