86 MENTAL EVOLUTION IN MAN 



" 3. Sounds which are rational but not articulate, ejacula- 

 tions by which we sometimes express assent to, or dissent 

 from, given propositions. 



"4. Sounds which are both rational and articulate, consti- 

 tuting true speech. 



" 5. Gestures which do not answer to rational conceptions, 

 but are merely the manifestations of emotions and feelings. 



"6. Gestures which do answer to rational conceptions, 

 and are therefore 'external,' but not oral manifestations of 

 the verbiim vioitale." 



To this list of the " Categories of Language " a seventh 

 must be added, to contain all kinds of written signs ; but with 

 such obvious addition I assent to the classification, as including 

 all the species that can possibly be included under the genus 

 Language, and therefore as excluding none. 



Now the first thing to be noticed is, that the signs made 

 may be made either intentionally or unintentionally; and 

 the next is, that the division of intentional signs may be 

 conveniently subdivided into two classes — namely, inten- 

 tional signs which are natural, and intentional signs which 

 are conventional. 



The subdivision of conventional signs may further be split 

 into those which are due to past associations, and those which 

 are due to inferences from present experience. A dog which 

 *' begs " for food, or a parrot which puts down its head to be 

 scratched, may do so merely because past experience has taught 

 the animal that by so doing it receives the gratification it 

 desires ; here is no need for reason — i.e. inference — to come into 

 play. But if the animal has had no such previous experience, 

 and therefore could not know by special association that such 

 a particular gesture, or sign, would lead to such a particular 

 consequence, and if under such circumstances a dog should 

 see another dog beg, and should imitate the gesture on 

 observing the result to which it led ; or if under such analogous 

 circumstances a parrot should spontaneously depress its head 

 for the purpose of making an expressive gesture, — then the 

 sign might strictly be termed a rational one. 



