8o THE SCIENCE OF LOGIC. 



We shall see in a later chapter (70) that there are ample grounds for 

 drawing a distinction between natural and artificial kinds or classifica 

 tions of things, but that it is the duty of the various other sciences, rather 

 than of logic, to say in particular cases what attributes are to be regarded as 

 essential for the specific nature of any individual thing, and, consequently, for 

 the connotation of its ordinary or lowest class name, the name one would 

 give in answer to the question : What is that thing ? 



But we must be careful to distinguish the logical use of the terms genus 

 and species from their use in the biological sciences. In these latter, species 

 means a group of individuals supposed to have descended from common an 

 cestors and to be indefinitely fertile in breeding among themselves ; genus 

 means the next highest group ; while under the species come the smaller 

 classes called varieties, and above the genera several wider classes called 

 tribes, orders, divisions, kingdoms etc. Logic calls all classes alike species 

 and genera, provided they fulfil the conditions indicated above. This, how 

 ever, must be borne in mind : that logical divisions, and, therefore, logical 

 genera and species, ought to aim at following the natural divisions of things 

 established in the natural (biological) and physical sciences (70). 



We can therefore maintain that our knowledge of things of the essences 

 of things is real knowledge, and not merely a knowledge of the meaning of 

 names (44), without denying the titles genus and species in the sense in 

 which these terms are used by modern logicians to subdivisions of what 

 earlier logicians regarded as species infimae. That men and monkeys are 

 different kinds or species of things zoologically and psychologically ; that they 

 differ in kind, 1 and not merely in the degree in which certain attributes or 

 qualities may be developed in either class ; that, on the other hand, monkeys 

 differ from dogs by a smaller diffc * .ice than that which separates either class 

 from men ; and that terriers differ Irom greyhounds by a still smaller differ 

 ence than either class does from monkeys : all these things we believe to be 

 true ; but to contend that their truth depends in any way upon the recognition 

 of the class &quot; man &quot; as a lowest logical species, or upon the recognition of the 

 &quot; existence of an absolute infima species,&quot;* is to confound two quite distinct 

 meanings of the same technical term the biological and the logical meanings. 

 We fail to see how the subdivision of the traditional species infima by modern 

 logicians necessarily involves a nominalistic or conceptualistic solution of 

 &quot; the whole question of the formation of universals &quot; or jeopardizes 

 &quot; the absolute character of truth &quot;. 3 If some modern logicians have 

 fallen into the errors just referred to, it is certainly not because they have 

 emphasized the sufficiently obvious fact that, whether we are concerned with 

 divisions above or below the traditional species infimae, the attribute which 

 forms the basis of any step in the process of division, and which is essential 

 to the sub-class or species constituting, as it does, the differentia specifica 

 of the latter is always and necessarily a separable accident of the class that 

 is being divided (the genus), and cannot, therefore, be essential to the latter. 



1 They differ, not merely specifically (&quot; in specie &quot;) but generically (&quot; toto genere 

 suo &quot;) in this case, for they have not even the same genus proximum : the genus 

 proximum of monkey being &quot;brute beast&quot; or &quot;animal irrationale&quot; which is a 

 co-ordinate species with &quot; man &quot; under the higher genus, &quot; animal &quot;. 



a CLARKE, Logic, p. 185. 3 ibid. 



