COMMON SENSE (aND SCIENCE ) 7 



posed as stages in the operations of the senses and the brain, but 

 simply as artifices of discussion: i.e., steps in the abstract analysis of 

 what is in practice an irreducibly integral (and ordinarily non- 

 reflective) process in which each "stage" presupposes or is presup- 

 posed by others. 



FROM STIMULI TO CONSTRUCTS 



Merely to see an object is no mean feat of organization. The meas- 

 ure of the achievement is indicated by the results of corneal trans- 

 plantation, giving sight to adults blind from birth. Young tells us: 



The patient on opening his eyes for the first time . . . reports only a 

 spinning mass of lights and colors. He proves to be quite unable to 

 pick out objects by sight, . . . His brain has not been trained in 

 the rules of seeing, does not know which features are significant and 

 useful for naming objects and conducting life. We are not conscious 

 that there are any such rules; we think that we see, as we say, "nat- 

 urally." But we have in fact learned a whole set of rules during child- 

 hood. 



At least a month passes before the subjects can recognize even a few 

 objects, and ". . . if sufficiently encouraged they may after some 

 years develop a full visual life and be able even to read." Making all 

 due allowance for the greater co-ordinative plasticity of infancy, still 

 we cannot but recognize that "seeing"— no simple passive reception 

 of an unequivocal signal— is a formulative process in which the re- 

 ceiver plays an active role. 



This conclusion is reinforced by the results of physiologic re- 

 search.* The eye contains some one hundred million separate recep- 

 tors. To "see" a thing must then demand some work of construction 

 from the myriad atomic stimuli. But even to speak of "construction 

 from atomic stimuli" is an oversimplification. Such stimuli are sep- 

 arately unknown to us; they are not facts but hypotheses. Weyl 

 argues that: 



Consciousness reacts with an entirety that is not merely a mosaic 

 composed of sensations; on the contrary, these so-called sensual data 

 are a subsequent abstraction. The assertion, that they alone are actu- 

 ally given and the rest is derivative, is not a description that care- 



* I must take cognizance of these results for, as becomes plain in Chapter XII, 

 I wish to maintain a realist position. 



