176 NAMES AND PROPOSITIONS. 



If, however, practical convenience is a sufficient 

 warrant for making the main demarcations in our 

 arrangement of objects run in lines not coinciding 

 with any distinction of Kind, and so creating genera 

 and species in the popular sense which are not genera 

 or species in the rigorous sense at all ; a fortiori must 

 we be warranted, when our genera and species are 

 real genera and species, in marking the distinction 

 between them by those of their properties which 

 considerations of practical convenience most strongly 

 recommend. If we cut a species out of a given 

 genus the species man, for instance, out of the genus 

 animal with an intention on our part that the pecu- 

 liarity by which we are to be guided in the application 

 of the name man should be rationality, then rationality 

 is the differentia of the species man. Suppose, how- 

 ever, that, being naturalists, we, for the purposes of 

 our particular study, cut out of the genus animal the 

 same species man, but with an intention that the 

 distinction between man and all other species of 

 animal should be, not rationality, but the possession 

 of " four incisors in each jaw, tusks solitary, and 

 erect posture." It is evident that the word man, 

 when used by us as naturalists, no longer connotes 

 rationality, but connotes the three other properties 

 specified ; for that which we have expressly in view 

 when we impose a name, assuredly forms part of the 

 meaning of that name. We may, therefore, lay it 

 down as a maxim, that wherever there is a Genus, and 

 a Species marked out from that genus by an assign- 

 able differentia, the name of the species must be 

 connotative, and must connote the differentia ; but 

 the connotation may be special, not involved in the 

 signification of the term as ordinarily used, but given 

 to it when employed as a term of art or science. 



