SECT. XVIII. 9. 10. ii. OF SLEEP. 



9. The great novelty of combination is owing to 

 another circumftance ; the trains of ideas, \vhich 

 are carried on in our waking thoughts, are in our 

 jdreams diffevered in a thoufand places by the fufpen- 

 fion of volition, and the abfence of irritative ideas, 

 and are hence perpetually falling into new catena- 

 tions. As explained in Sect. XVI. i. 9. For the 

 power of volition is perpetually exerted dining our 

 .waking hours in comparing our pafling trains of 

 ideas with our acquired knowledge of nature, and 

 thus forms many intermediate links in their catena- 

 tion. And the irritative ideas excited by the ftimulus 

 of the objects, with which we are furrounded, are 

 every moment intruded upon us, and form other 

 links of our unoeafing catenations of ideas 



ip. The abfencc of the ftimuli of external bodies, 

 and of volition, in our dreams renders the organs 

 of fenfe liable to be more ftrongly affected by the 

 powers of fenfation, and of ailociation. For onf 

 defires or averfions, or the obtrufions of furround- 

 ing bodies, diifever the fenfitive and aflbciate tribes 

 of ideas in our waking hours by introducing thofe 

 of irritation and volition amongft them. Hence 

 proceeds <the fuperior diftinctnefs of pleafurable or 

 painful imagery in our fleep ; for we recai the figure 

 and the features of a long loft friend, whom we 

 loved, in our dreams with much more accuracy and 

 vivacity than in our waking thoughts. This circum- 

 flance contributes o prove, that our ideas of ima- 

 gination are reiterations of thofe motions of our 

 organs of fenfe, which were excited by external 

 objects ; becaufe while we are expofed to the ftimuli 

 of prefent objects, our ideas of abfent objects can- 

 not be fo diftinctly formed. 



1 1. The rapidity of the fucceilion of tranfactions 

 in our dreams is almoft inconceivable ; infomuch 

 that, when we are accidentally awakened by the 



jarring 



