BOOK V, 



FOEMAL ASTKONOMY 



CHAPTER I. 

 Prelude to Copernicus. 



Nicolas of Cus. 



WILL quote the passage, in the writings of this author, which 

 -L bears upon the subject in question. I translate it from the edition 

 of his book De Docta Ignorantia, from his works published at Basil 

 in 1565. He praises Learned Ignorance — that is, Acknowledged Ig- 

 norance — as the source of knowledge. His ground for asserting the 

 motions of tbe earth is, that there is no such thing as perfect rest, or 

 an exact centre, or a perfect circle, nor perfect uniformity of motion. 

 " Neque verus circulus dabilis est, quinetiam verior dari possit, neque 

 unquam uno tempore sicut alio a3qualiter prsecise, aut movetur, aut 

 circulum veri similem, aequalem describit, etiamsi nobis hoc non ap- 

 pareat. Et ubicumque quis fuerit, se in centro esse credit." (Lib. i. 

 cap. xi. p, 39.) He adds, " The Ancients did not attain to this knowl- 

 edge, because they were wanting in Learned Ignorance. Now it is 

 manifest to us that the Earth is truly in motion, although this do not 

 appear to us ; since we do not apprehend motion except by comparison 

 with something fixed. For if any one were in a boat in the middle of 

 a river, ignorant that the water was flowing, and not seeing the banks, 

 how could he apprehend tbat the boat was moving ? And thus since 

 every one, whether he be in the Earth, or in the Sun, or in any other 

 star, thinks that he is in an immovable centre, and that every thing 

 else is moving ; he would assign different poles for himself, others as 

 being in the Sun, others in the Earth, and others in the Moon, and so 

 of the rest. Whence the machine of the world is as if it had its cen- 

 tre everywhere and its circumference nowhere." This train of thought 



