470 OPERATIONS SUBSIDIARY TO INDUCTION. 



out rendering any received assertions inadmissible, the name can be de- 

 fined in accordance with its received use, which is vulgarly called defining 

 not the name but the thing. What is meant by the improper expression 

 of defining a thing (or rather a class of things — for nobody talks of defin- 

 ing an individual), is to define the name, subject to the condition that it 

 shall denote those things. This, of course, supposes a comparison of the 

 things, feature by feature and property by property, to ascertain what at- 

 tributes they agree in ; and not unfrequently an operation strictly induc- 

 tive, for the purpose of ascertaining some unobvious agreement, which is 

 the cause of the obvious agreements. 



For, in order to give a connotation to a name, consistently with its de- 

 noting certain objects, we have to make our selection from among the vari- 

 ous attributes in which those objects agree. To ascertain in what they do 

 agree is, therefore, the first logical operation requisite. When this has 

 been done as far as is necessary or practicable, the question arises, which 

 of these common attributes shall be selected to be associated with the 

 name. For if the class which the name denotes be a Kind, the common 

 properties are innumerable ; and even if not, they are often extremely nu- 

 merous. Our choice is first limited by the preference to be given to prop- 

 erties which are well known, and familiarly predicated of the class ; but 

 even these are often too numerous to be all included in the definition, and, 

 besides, the properties most generally known may not be those which serve 

 best to mark out the class from all others. We should therefore select 

 from among the common properties (if among them any such are to be 

 found) those on which it has been ascertained by experience, or proved by 

 deduction, that many others depend ; or at least which are sure marks of 

 them, and from whence, therefore, many others will follow by inference. 

 We thus see that to frame a good definition of a name already in use, is 

 not a matter of choice but of discussion, and discussion not merely respect- 

 ing the usage of language, but respecting the properties of things, and 

 even the origin of those properties. And hence every enlargement of 

 our knowledge of the objects to which the name is applied, is liable to 

 suggest an improvement in the definition. It is impossible to frame a per- 

 fect set of definitions on any subject, until the theory of the subject is per- 

 fect ; and as science makes progress, its definitions are also progressive. 



§ 4. The discussion of Definitions, in so far as it does not turn on the 

 use of words but on the properties of things, Dr. Whewell calls the Expli- 

 cation of Conceptions. The act of ascertaining, better than before, in what 

 particulars any phenomena which are classed together agree, he. calls in his 

 technical phraseology, unfolding the general conception in virtue of which 

 they are so classed. Making allowance for what appears to me the dark- 

 ening and misleading tendency of this mode of expression, several of his 

 remarks are so much to the purpose, that I shall take the liberty of tran- 

 scribing them. 



He observes,* that many of the controversies which have had an impor- 

 tant share in the formation of the existing body of science, have " assumed 

 the form of a battle of Definitions. For example, the inquiry concerning 

 the laws of falling bodies led to the question whether the proper definition 

 of a uniform force is that it generates a velocity proportional to the space 

 from rest, or to the time. The controversy of the vis viva was what was 



* Novum Organum Renovatum, pp. 35-37. 



