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III. Statement by Mr. J. Guild. 



Are Sensation Intensities Measurable ? 



I have been invited to present the case of those members of this Com- 

 mittee whose answer to the question : Are sensation intensities measurable ? 

 is in the negative. To write a report truly representative of the views and 

 outlook of those members would have involved an amount of collaboration 

 which for geographical and other reasons has been quite impracticable. 

 I have therefore made no attempt at such collaboration and this section of 

 the Report is simply an exposition of my own views. But though I am aware 

 that some of my colleagues would approach the problem from quite different 

 angles I am not aware of any significant respect in which their main con- 

 clusions would differ from mine. In respect of these main conclusions I 

 am confident that this section of the Report is representative of the con- 

 sidered opinions of the majority of the physicists on the Committee. 



It is necessary in dealing with a subject of this kind to discuss not only 

 physical but psychological matters. I cannot claim that in dealing with the 

 latter the terminology is always employed in exactly the same sense as it 

 would be used in the literature of psychology. I must plead with psycho- 

 logists for the same tolerance in this respect that physicists have to extend 

 to them when perusing their writings on psycho-physical problems. I have 

 tried as far as possible to ensure that my meaning shall be clear from the 

 context despite probable inaccuracies in psychological terminology. I am 

 also dealing with broad principles, and to avoid confusion it has been 

 necessary to abstain from frequent digressions to mention and explain away 

 minor matters of detail which may not be in exact accord with some general 

 statement. There are practically no physical or psycho-physical phenomena 

 which are accurately described by any general statement. For example, I 

 describe a ' permanent object ' as a relation structure in which all the rela- 

 tions are found to be the same at all times. Of course there is not, strictly 

 speaking, any such thing : temperature variations and other causes produce 

 minor variations of relation-structure in any so-called permanent object. 

 Points of this kind have no relevance to our present discussion and it would 

 merely cloud the issue to bother about them. I trust this will be borne in 

 mind by anyone who inay consider that any statement or definition made 

 hereafter is not quite right. I have also been confronted with the difficulty, 

 in writing for readers whose experience is mainly derived from two different 

 fields of study, of deciding what may be taken for granted. I trust this will 

 be sufficient justification if I appear to any reader, or section of readers, to 

 indulge in over-elaboration of obvious points. The same points may not 

 be familiar to all. 



Measurement. 



Before proceeding to consider the problem of measurement as applied to 

 psycho-physical problems it is desirable to consider some of the general 

 principles of measurement . 



Measurement is primarily a device which enables us to use the laws of 

 arithmetic to solve problems relating to phenomenal events. The laws of 



