4* IRRITATIVE MOTIONS. SECT. VII. 3. 



And when the pharynx is irritated by agreeable 

 food, the mufcles of deglutition are brought into 

 action by aflbciation. Thus when a greater light 

 falls on the eye, the iris is brought into action with- 

 out our attention ; and the ciliary procefs, when 

 the focus is formed before or behind the retina, by 

 their aflbciations with the increafed irritative mo- 

 tions of the organ of vifion. Many common ac- 

 tions of life are produced in a fimilar manner. If 

 a fly fettle on my forehead, whilft I am intent on 

 my prefent occupation, I diflodge it with my finger, 

 without exciting my attention or breaking the train 

 of my ideas. 



2. In like manner the irritative ideas fuggeft to 

 us many other trains or tribes of ideas that are af- 

 fociated with them. On this kind of connection, 

 language, letters, hieroglyphics, and every kind of 

 fymbol, depend. The iymbols themfelves produce 

 irritative ideas, or fenfual motions, which we do 

 not attend to ; and other ideas, that are fucceeded 

 by fenfation, are excited by their aflbciation with 

 them. And as thefe irritative ideas make up apart 

 of the chain of our waking thoughts, introducing 

 other ideas that engage our attention, though them- 

 felves are unattended to, we find it very difficult to 

 inveftigate by what fteps many of our hourly trains 

 of ideas gain their admittance. 



It may appear paradoxical, that ideas can exift, 

 and not be attended to ; but all our perceptions are 

 ideas excited by irritation, and fucceeded by fenfa- 

 tion. Now when thefe ideas excited by irritation 

 give us neither pleafure nor pain, weceafe to attend 

 to them. Thus whilft 1 am walking through that 

 grove before my window, I do not run againft the 

 trees or the benches,^ though my thoughts are ftre- 

 nuoufly exerted on fome other object. This leads 

 us to a diftinct knowledge of irritative ideas, for the 

 idea of the tree or bench, which I avoid, exifts on 



my 



