ADVANCEMENT OF LEARNING 81 



on account of the extreme prejudice and danger which both 

 religion and philosophy hence incur, because a mixture of these 

 makes both a heretical religion and a fantastic and supersti- 

 tious philosophy.c 



It is otherwise, as to the nature of spirits and angels; this 

 being neither unsearchable nor forbid, but in a great part level 

 to the human mind, on account of their affinity. We are, in- 

 deed, forbid in Scripture to worship angels, or to entertain fan- 

 tastical opinions of them,d so as to exalt them above the 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 their 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 understood of revolted or unclean spirits : con- 

 versation 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 illu- 

 sions, appear from Scripture, reason, and experience, to be no 

 small part of spiritual wisdom. Thus says the apostle, "Strate- 

 gematum ejus non ignari sumus."' 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 III 



Natural Philosophy divided into Speculative and Practical. The 

 Necessity of keeping these Two Branches distinct 



But to leave natural theology, and proceed to natural philoso- 

 phy ; 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, imitating 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 philosophers, miners, and smelters intro- 

 duced ? This, indeed, may appear jocular, yet such a kind of 

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