Chap. III. ANTIENT METAPHYSICS. 17 



ftate, decay, and at laft are totally dlflfolved. Now, this progrefs alfo 

 is fuch a change as I call motion ; and thus far we fee from ivhat^ to 

 ivhat the change is ; for it is from a ftate of perfection to a ftate of 

 decay and diffolution. 



Here our idea of motion begins to be more full and compleat. 

 But, in the other cafe of the progrefs towards perfedion, it is not fo 

 compleat ; becaufe we have hitherto difcovered to ivhat the change is, 

 but lioifrom ivhat. 



In order to find out this, we muft make a diftindlon, well known 

 in antient philofophy, but which our modern philofophers hardly e- 

 ver mention ; the diftindion I mean Is betwixt actual exiftence, or 

 exifting evEpy«^, as Ariftotle has exprefled it, and exifting only potenti- 

 ally, that is, In poiver or capacity. This, however, is a diftindlion 

 which runs through all nature and art ; and, without which, it is im- 

 poffible to explain perfedly many things in the fyftem of nature. 

 But, as it is fo little known, fome words will be neceflary to explain 

 it. 



That every thing exifting, whether by nature or art, was, before 

 it exifted, poflible to exift, is evident; for it could never have exiftcd, 

 if it had not been fir ft in the poijuer or capacity of exifting ; and, as 

 every thing both ot nature and art is produced by certain determinate 

 caufes, the prodndions both of nature and art are faid, with proprie- 

 ty enough, to exift potentially in thofe caufes, even before they are 

 produced. And thus, things do in fome forr exift, even before they 

 exift : hut then this exiftence is very dift'erent iro.-u that ftate of per- 

 fedtion above mentioned, to which waeu tiie tiiin.; is i'rvived, it is 

 faid to exift a^fually, adlu, et non-puteutia ; 01, as Ariil^ tic l.ab exprefled 

 it, ev^pyH*, a vvt^rd which he has ukd lo exprefs rhis kind of cxiftcnce, 

 which is beft ihown by its energies 01 operations. 



C The 



