VI. 



THE NEBULAR HYPOTHESIS. 



INQUIRING into the pedigree of an idea is not a bad 

 means of roughly estimating its value. To have come of 

 respectable ancestry, is 2:>rimd facie evidence of worth in a 

 belief as in a person ; while to be descended from a discred- 

 itable stock is, in the one case as in the other, an unfavora- 

 ble index. The analogy is not a mere fancy. Beliefs, to- 

 gether w^ith those who hold them, are modified little by ht- 

 tle in successive generations ; and as the modifications 

 which successive generations of the holders undergo, do 

 not destroy the original type, but only disguise and refine 

 it, so the accompanying alterations of belief, however much 

 they purify, leave behind the essence of the original belief. 

 Considered genealogically, the received theory respecting 

 the creation of the Solar System is unmistakeably of low 

 origin. You may clearly trace it back to primitive mythol- 

 ogies. Its remotest ancestor is the doctrine that the celes- 

 tial bodies are personages who originally lived on the Earth 

 — a doctrine still held by some of the negroes Livingstone 

 visited. Science having divested the sun and planets of 

 their divine personalities, this old idea was succeeded by 

 the idea which even Kepler entertained, that the planets 

 are guided in their courses by presiding spirits ; no longer 



