OF KNOWLEDGE. 11 



or oil of roses to the atmosphere) smelt that per- 

 fume, except where roses were near us, whether 

 within our sight or not, we have learned by the 

 judgment of our minds to associate the smell with 

 the flowers ; and can no more refrain from think- 

 ing it the smell of roses, than we can from per- 

 ceiving the perfume. 



In the case of the songs of the birds, there is 

 another organ affected, but the process is the 

 same : the ear never hears such sounds, unless 

 there are birds in the case, or some substitute for 

 birds, which is explainable in some other way; 

 and, therefore, we no more doubt that that song 

 is the song of the birds than we can doubt that 

 we are hearing a song. 



So also, if we lay our hand upon any substance, 

 as a piece of woollen cloth or a piece of iron, or 

 taste any substance, as a bit of bread or of sugar, 

 if we have been formerly acquainted with that sub- 

 stance, and have been accustomed to call it by that 

 name, we can no more deny that it is the sub- 

 stance than we can deny our own existence. 



These matters may seem to be so simple, and so 

 self-evident, that it is a waste of time to write them 

 down, or to read them after they are written. 

 But that is an error; and it is the error which 

 keeps very many of us in ignorance, and makes us 

 listless, and even vicious, when we otherwise 

 might be occupied, happy, and doing right. That 

 which we already know is the instrument, and the 

 only instrument with which we can "work out" 

 more knowledge, and turn it to account ; and our 

 senses, or organs of OBSERVATION, are the only 

 means through which that instrument can work. 



Those organs of observation will not cease from 



