EMPIRICAL TOOLS AND EMPIRICISM 145 



choose the larger of two surfaces; it is extraordinarily hard to get 

 him to choose a particular size, except when differences are very 

 great. 



Just so, many of us easily detect a flat note in a continuing melody, 

 but very few of us possess absolute pitch. 



At one extreme of the spectrum of denotative clarity, the concepts 

 of physics most often have precise, instrumentally established denota- 

 tions. At the other extreme, few instruments are deployed in psy- 

 chiatry, but the notorious nebulosity of its fundamental concepts 

 stems ultimately from an almost complete (and unavoidable?) fail- 

 ure to create an acceptable body of external standards of reference. 

 In the broad spectrum of denotative clarity the position of a given 

 concept is then primarily correlated with the availability of such 

 standards, and only secondarily with the availability of the instru- 

 ments that make comparisons. There is no magic in the instrument as 

 such. Where no external standard exists, no instrument can help us; 

 and, however convenient in practice, the instrument is wholly super- 

 fluous in principle where we do not need it to make adequate 

 comparisons. 



''Things" as standards. A standard weight is a reference "thing" 

 used in quantitative comparisons, but in many other cases only 

 qualitative comparison is required, or even meaningful. Wishing to 

 know whether a given specimen "belongs" to some previously de- 

 scribed species or subspecies, the taxonomist supplements his mental 

 image of the possibilities by making point-by-point comparisons be- 

 tween his specimen and tliose available in museum collections. Due 

 to the intrinsic variability of living organisms, high-precision quanti- 

 tative comparisons are here unlikely to be helpful. The taxonomist 

 must then exercise his judgment within a penumbra of uncertainty 

 the extent of which is, however, very much reduced by the avail- 

 ability of reference "things." 



Sometimes almost purely qualitative comparison is completely 

 definitive. Consider an organic chemist who wishes to know whether 

 a synthetic compound (X) in his test tube is or is not a certain 

 previously isolated natural product (P). With the aid of elaborate in- 

 struments he can compare various properties of X and P, but actually 

 he regards as most definitive a procedure involving only the simplest 

 of instruments, and not even requiring quantitative measurements. 

 This is the technique of the "mixed melting point." Ha\'ing found 



