240 ANTIENT METAPHYSICS. Book IV. 



nourlfliment we take in, and afcend to the head, which they make 

 heavy and unable to fuflam iifelf ; then returning back again, and 

 going downward, they produce Sleep *. 



Having thus fliown what Sleep is, namely, that it is a Cellation 

 of the Adion of our Senfes, proceeding from the wearinefs of Na- 

 ture, we are next to confider what Dreaming is, and to diftinguifli 

 it from fome phacnomena which appear to be Dreams, but are not. 

 And, in the firft place, it is agreed by all, that we can only be faid 

 properly to dream when we are afleep ; and therefore thofe Vifions 

 I juft now mentioned, which a man has in a fainting fit, are not 

 dreams, though they be the operations of the Phantafia, bccaufe wc 

 are not then afleep. 



Secondly^ Thofe perceptions above mentioned, of Light, orNoife, 

 which fome people have while they feem to be afleep, are not Dreams, 

 for the fame reafon, and likewife for another reafon, namely, that 

 they are the perceptions, by the Senfes, of objedls of Senfe adlually 

 prefent, confequently not the operations of the Phantafia, which all 

 dreams mufl: necefl'arily be. 



But, 3//0, Even all Phantafms in our Sleep, though they be the- 

 operations of the Phantafia, are not Dreams, unlefs the Mind be de- 

 ceived by them, and believe them to be real exiftences ; for, if the 

 Mind tell itfelf, as it fometimes does, that this is but a Dream and a 

 Delufion, then it is not, properly fpeaking, a Dream, but fuch an I- 

 magination as we have when we are awake and in our fober Sen- 

 fes f. And the reafon is, as Ariflotle has told us, that we are not 

 then perfedtly afleep ; becaufe the governing principle in us is adive, 



and 



* Ibid. cap. 3. 



t Arift, de Infomniis, cap. 3. in medio. 



