122 ADV AX CEMENT OP LEARNlKG. [BOOK 111 



above tho degree of creatures, or to think of them higher 

 than we have reason ; but the sober inquiry about them, 

 which either ascends to a knowledge of tlieir nature by the 

 scale of corporeal beings, or views them in the mind, as in a 

 glass, is by no means forbid. The same is to be undei'stood 

 of revolted or unclean spirits : conversation with them, or 

 using their assistance, is unlawful ; and much more in any 

 manner to worship or adore them : but the contemplation 

 and knowledge of their nature, power, and illusions, appears 

 i'rom Scripture, reason, and experience, to be no small part 

 of spiritual wisdom. Thus says the apostle, " Sti-ategematum 

 ejus non ignari sumus."o And thus it is as lawful in natural 

 theology to investigate the nature of evil spirits, as the 

 nature of poisons in physics, or the nature of vice in morality. 

 But this part of knowledge relating to angels and spirits^ 

 which we call the appendage to natural theology, cannot be 

 noted for deficient, as having been handled by many ; but we 

 may justly tax no small part of the writers in this way, 

 either with levity, superstition, or fruitless speculation. 



CHAPTER ITI. 



Natural Philosophy divided into Speculative and Practical. The Neces- 

 sity ot keeping these Two Branches distinct. 



But to leave natural theology, and proceed to natural 

 philosophy ; as it was well said by Democritus, that " the 

 knowledge of nature lies concealed in deep mines and caves ;"^ 

 and by the alchemists, that "Vulcan is a second nature, imi- 

 tating concisely what the first takes time and circuit to 

 effect ;"^ suppose natural philosophy were divided, as it 

 regards the mine and the furnace, and two offices of phi- 

 losophers, miners and smelters introduced ? This, indeed, 

 may appear jocular, yet such a kind of division we judge 

 extremely useful, when proposed in just and familiar terms ; 

 so that the doctrine of nature be divided into speculative and 

 practical, or the search after causes, and the production of 

 effects : the one entering into the bowels of nature, and the 

 otlicr forming her upon the anvil. !Nor are we insensible of 



t 2 Cor. ii. 11. ■ Laertius, Life o.^ Seneca. 



•* Paracelsus de Philos. Sagac. r 



