374 REFLEX ACTION, INSTINCT, AND REASON 



act voluntarily. It may be so strong as to be irresistible, in which 

 case it enlists a corresponding strength of will. Desire cannot be 

 awakened except by present or prospective pleasure or pain 

 not necessarily ' physical ' pleasure or pain, but pleasure or pain of 

 some sort for example a whimsical pleasure in demonstrating 

 that we are able to disregard ' physical ' pain, in which case the 

 desire to achieve the pleasure transcends the desire to avoid the 

 pain. 



6 1 8. An instinct may be defined as an ' innate and inherited ' mental 

 impulse or inclination to do a certain definite act, the instinctive act, 

 on receipt of a certain definite stimulus. Therefore it is a mental 

 character which is developed in the individual under the stimulus 

 of nutriment, but which is awakened to activity by experience (the 

 appropriate stimulus). For example, the sexual instinct is an 

 ' innate ' character that is aroused by the presence of an individual 

 of the opposite sex. I think psychologists believe instinctive 

 actions to be types of reflex action only because, when studying 

 the question, they have limited their attention mainly to the 

 instincts of the lower animals. We have then, very often, no 

 means of knowing whether any given action is, or is not, prompted 

 by desire and directed by the will. But when we consider our 

 own instincts we are on safer ground. Our knowledge is not 

 then derived by inference from the actions of another animal, but 

 from actual experience of the mental phenomena. We know 

 our own instincts therefore with an intimacy with which we 

 cannot know those of the lower animals, amongst which all our 

 own instincts have their counterparts. Consequently it is safer to 

 reason from our instincts to those of lower animals than to 

 adopt the reverse process. Since we are derived from lower types, 

 presumably, our instincts are of the same nature. They may 

 differ in degree, they can hardly differ in kind. 



619. Consider, then, our own instincts, for example the instinct 

 to sleep periodically, to rest when tired, to sport when rested, to 

 eat and drink when hungry and thirsty, the instincts of imitative- 

 ness and curiosity, and the deferred instincts of sexual and 

 parental love. In the case of each we feel strongly, if sometimes 

 vaguely, the prompting desire to seek pleasure or to avoid pain 

 which is the actual and direct stimulus of the will to do, which, in 

 turn initiates the instinctive act, and which therefore sharply 

 differentiates it from the reflexes which are never directly prompted 

 by the desire to do an action. Thus, sleepiness prompts us, 

 strongly inclines us, voluntarily to assume attitudes of repose, as 



