36 ASSOCIATE MOTIONS. SECT. X, 3. 3. 



The facility, with which each mufcle changes from one affo- 

 ciated tribe to another, and that either backwards or forwards, 

 is well obfervable in the mufcles of the arm in moving the wind- 

 Jafs of an air-pump ; and the ilownefs of thofe mufcular move- 

 ments, that have not been affociated by habit, may be experi- 

 enced by any one who (hall attempt to faw the air quick per- 

 pendicularly with one hand, and horizontally with the other at 

 the fame time. 



3. In learning every kind of fcience we voluntarily affociate 

 many tribes and trains of ideas, which afterwards are ready for 

 all the purpofes either of volition, fenfation, or irritation ; and 

 in fome inftances acquire indhToluble habits of afting together, 

 fo as to affect our reaioning, and influence our actions. Hence 

 the neceffify of a good education. 



Thefe affociate ideas are gradually formed into habits of al- 

 ing together, by frequent repetition, while they are yet feparately 

 obedient to the will , as is evident from the difficulty we experi- 

 ence in gaining fo exacft an idea of the front of St. Paul's church, 

 as to be able to delineate it with accuracy, or in recollecting a 

 poem of a few pages. 



And thefe ideas, thus affociated into tribes, not only make up 

 the parts of the trains of volition, fenfation, and irritation ; but 

 the fame idea compofes a part of many different tribes and trains 

 of ideas. So the fimple idea of whitenefs compofes a part of the 

 complex idea of fnow, milk, ivory ; aiid the complex idea of the 

 letter A compofes a part of the feveral affociated trains of ideas 

 that make up the variety of words, into which this letter enters. 



The numerous trains of thefe affociated ideas are divided by 

 Mr. Hume into three claffes, which he has termed contiguity, 

 caufation, and refemblance. Nor fhould we wonder to find 

 them thus connected together, fince it is the bufmefs of our 

 lives to difpofe them into thefe three claffes ; and we become 

 valuable to ourfelves and our friends, as we fucceed in it. Thofe 

 \vho have combined an extenfive clafs of ideas by the contiguity 

 of time or place, are men learned in the hiftory of mankind, and 

 of the fciences they have cultivated. Thofe who have conneft- 

 ed a great clafs of ideas of refernblances, poffefs the fource of 

 the ornaments of poetry and oratory, and of all rational analo- 

 gy. While thofe who have conne&cd great claffes of ideas of 

 caufation, are furnifhcd with the powers of producing effects. 

 Thefe are the men of aftive wifdom, who lead armies to victory, 

 and kingdoms to profperity ; or difcover and improve the fci- 

 ences, which meliorate and adorn the condition of humanity. 



SECT. 



