QUANTITATIVE ESTIMATES OF SENSORY EVENTS 315 



ments the instructions are of vital importance because there are several 

 diflferent things the observer may do depending on his interpretation of 

 them, in the present case the nature of the instructions has no influence 

 on the experiment because there is only one thing the observer can do if he 

 performs the experiment at all. 



The foregoing is, in all essentials, an exact description of how experi- 

 ments of this kind are carried out. The extension of the process to build 

 up a series of stimulus intervals each of which is related to the next in order 

 in the same way as y4 .jB is related to B.C clearly implies no new principle. 

 The application of equivalent processes to hearing or other senses only 

 involves differences in practical details. 



We observe that the experiment may be described without introducing 

 the concepts of equality, difference, bisection, etc. The only concept 

 required is that of ' recognisability ' as something which confers on some 

 relations a unique significance not possessed by other relations of the same 

 general type. We also note that it has been unnecessary to make specific 

 mention of sensation intensities. In our description sensations remain in 

 the background, as they do in ordinary life, serving their normal purpose 

 of making us aware of phenomenal relations among the objects in the 

 perceptual field. Of course there must be psychological relations corre- 

 sponding in some way to the observed phenomenal relations, but we pay no 

 attention to these in performing the experiment ; we simply accept the 

 information they afford us about the external objects. The mental attitude 

 of the observer during these observations is the normal one of perception, 

 not of apperception. He is observing the objects, not his own sensations : 

 his criterion of the accomplisliment of his task is not the deliberate 

 identification of any unique relation among his sensations, but the recog- 

 nition of a unique relation exhibited by the objects. 



Recognition appears to me to be the key-word for the interpretation of 

 this experiment. What does recognition mean ? We may confine atten- 

 tion to the intuitive recognition oi phenomena, the kind of thing that happens 

 when I know a friend as soon as I see him, or when I know my own house 

 as soon as I come within sight of it, or know that a certain sound is the call 

 of the cuckoo as soon as I hear it, or know tea by its taste, or lavender by 

 its smell, and so on. What is my friend, what is my house, what is a 

 cuckoo, or tea, or lavender ? Each of these is nothing more (at least as 

 far as I am concerned) than permanent, or quasi-permanent, relation- 

 structures perceivable against a background of ever-changing phenomenal 

 relations. We look out (and hear out, feel out, taste out, and smell out) 

 on a world consisting of a medley of directly perceivable phenomenal 

 relations of a great variety of diflferent kinds. Some of these relations keep 

 changing and attract but fleeting attention. Others remain apparently 

 unchanged for a long time, and these we group into relation structures 

 which constitute enduring phenomena such as people, houses, cuckoos, 

 tea and so on, the ' objects ' or ' things ' which endure. Now any such 

 relation structure may contain many diflferent types of relation. Not all 

 of these involve magnitudes, but many of them do, and of these some will 

 be extensive, like length, mass, brightness, etc. Of the relations involving 

 such magnitudes, some will involve absolute extension while others will 

 involve only relative extensions. Absolute is here used in the ordinary 

 everyday sense. There is, of course, no criterion for absolute extension of 

 any magnitude in the fundamental sense of absolute. Absolute extension 

 in the ordinary sense is itself relative — relative to some universally applicable 

 standard, such as the length of the standard metre, or the mass of the 

 standard gram, or the brightness of a surface emitting a lumen per sq. cm., 



