6 INTRODUCTION. 



or thing having no parts, from a line. But further, as it is admitted 

 by all philofophers, that all the bodies on this earth, however dif- 

 ferent in appearance, are refolvable into four •elemental bodies, earth, 

 water, air, and fire, there appears to be nothing in the nature of 

 things to hinder thefe four from being refolved into one matter 

 common to them all. And if it be true, as I believe it is, that thofe 

 elements change into one another, there muft neceflarily be in 

 them fome common matter, vs'hich, by afluming different forms, be- 

 comes fire, air, earth, or water *. 



As to the Formal caufe, it is explained at great length in Archy- 

 tas the Pythagorean's work, irspi rov iravroi^ the fubje(5l of which is, 

 tiniverfal forms ^ as I call them, (for generals are the fubjed of all 

 fciences, but unmerfuls are the proper fubjed of metaphyfics), and 

 Ariftotle's book of Categories, where we have all the different caufes 

 of that kind enumerated and reduced to the number of lo. It is 

 perhaps the greateft work of fcience that ever was compofed ; and 

 indeed it is the foundation of all fcience, fince, without it, there can- 

 not be any complete definition f. It is fuch a difcovery as, I think, 

 could not have been made by any fingle man, but only by focieties 

 of men, fuch as the Egyptian priefts, who had been cultivating 

 fciences for thoufands of years. Though it treats only of the forms 

 of things, yet, as thefe are fo infinitely various, and belong to every 

 thing in heaven or earth, making an eflential part of the fyftem of 

 the univerfe, they are a very proper fubjecl of univerfal philofophy 

 or metaphyfics. And accordingly, Archytas has very properly en- 

 titled his work, Of the whole of things. And Ariftotle, though he 

 has made his book of Categories a part of his Logic, and the firfk 

 part, for which, I think, there was -a very good reafon, he has like- 

 wile treated of them in his Metaphyfics. 



The 



* See Vol. I, p. 48. 

 t Ibid. p. 317. 



