1 8 MOTIONS OF SECT. III. 6. i . 



come more rigid, are rendered lefs fufceptible of new habits of 

 motion, though they retain thofe that were before eftablifhed. 

 This is fenfibly obferved by thofe who apply themfelves late in 

 life to mufic, fencing, or any of the mechanic arts. In the fame 

 manner many elderly people retain the ideas they had learned 

 early in life, but find great difficulty in acquiring new trains of 

 memory ; infornuch that in extreme old age we frequently fee 

 a forgerfulnefs of the bufinefs of yefterday, and at the fame time 

 a circumftantial remembrance of the amufements of their youth ; 

 till at length the ideas of recollection and activity of the body 

 gradually ceafe together, fuch is the condition of humanity ! 

 and nothing remains but the vital motions and fenfations. 



VI. i. In oppofition to this doctrine of the production of 

 our ideas, it may be afked, if fome of our ideas, like other ani- 

 mal motions, are voluntary, why can we not invent new ones, 

 that have not been received by perception ? The anfwer will be 

 better underftood after having perufed the fucceeding fection, 

 where it will be explained, that the mufcular motions like wife 

 ar.e originally excited by the ftimulus of bodies external to the 

 moving organ ; and that the will has only the power of repeat- 

 ing the motions thus excited. 



2 Another objector may afk, Can the motion of an organ of 

 fenfe refemble an odour or a colour ? To which I can only an- 

 fwer, that it has not been demonftrated that any of our ideas re- 

 femble the objects that excite them ; it has generally been be- 

 lieved that they do not ; but this (hall be difcufled at large in 

 Sea. XIV. 



3. There is another objection that at fir ft view would feem 

 lefs eafy to furmount. After the amputation of a foot or a finger, 

 it has frequently happened, that an injury being offered to 

 the (lump of the amputated limb, whether from cold air, 

 too great preffure, or other accidents, the patient has com- 

 plained of a fenfation of pain in the foot or finger, that was 

 cut off. Does not this evince that all our ideas are excited in 

 the brain, and not in the organs of fenfe ? This objection is 

 anfwered, by obferving that our ideas of the (hape, place, and 

 folidity of our limbs, are acquired by our organs of touch and 

 of fight, which are fituated in our fingers and eyes, and not by 

 any fenfations in the limb itfelf. 



In this cafe the pain or fenfation, which formerly has arifen 

 in the foot or toes, and been propagated along the nerves to the 

 central part of the fenforium, was at the fame time accompanied 

 with a vifible idea of the fhape and place, and with a tangible 

 idea of the folidity of the affefted limb : now when thefe nerves 

 are afterwards affected by any injury done to the remaining 



ft iimp 



