MENTAL OPERATIONS IX RELATION TO TIME. 109 



are capable of being thus quickened and invigorated 

 by intellectual society and struggle are seen or felt 

 to decline in power when brought into contact with 

 feebler intellects and frivolous subjects of thought. 

 Such instances are familiar to all who take even 

 ordinary note of mental phenomena in themselves and 

 others. The mind rises or falls from the conditions to 

 which it is subjected. 



This whole subject of its transient states is, in truth, 

 a very curious one, and not, I think, adequately studied. 

 It embraces, of course, not merely momentary changes 

 like those just described, but those larger fluctuations 

 which the totality of life brings before us changes 

 belonging to the different ages of man, the appurte- 

 nance of poetry as well as philosophy, and finely por- 

 trayed by the genius of Horace and Shakespeare. But 

 the daily and hourly fluctuations of state are those of 

 most import to the philosophy of mind. Eochefoucauld 

 says, and truly, ' On est quelquefois aussi different de 

 soi-meme que des autres.' We speak of the mind as a 

 unit, and in the broad sense of personal identity it is 

 so. But within this individuality lie those many and 

 ever-changing diversities of intellect and feelings which 

 enter into the current of each single life. Observation 

 unceasingly tells us of the influences alike of external 

 and internal causes in producing these transient states 

 of mind. Hunger and satiety, heat and cold, fatigue 

 and repose, exuberant health and the languor of dis- 

 ease, are the commonplace interpreters of the fact. 

 Opium, wine, and the other narcotics and stimulants, 

 each has its peculiar effect for a time on this the higher 



