16 PROGRESS OF HUMAN KNOWLEDGE. 



not indeed by any obvious or certain law, but under 

 conditions analogous to those by which bodily like- 

 ness is transmitted to successive generations. 



I have been illustrating the progress of human 

 knowledge chiefly through the physical sciences ; and 

 this, in truth, is almost a necessity of the subject. It 

 can hardly be affirmed that mere speculative thought, 

 apart from material research, takes a wider or bolder 

 form than it did in the ancient philosophy. There 

 is scarcely a single hypothesis, whatever the subject, 

 which has not some prototype, more or less defined, 

 in one school or other of the Greek, Roman, or 

 mediaeval ages. Man, Mind and Matter, Life, Death 

 and Futurity, the Nature of the Deity, the Origin of 

 Evil, &c., furnished to them, as to us, problems upon 

 which all who have capacity for thought are in some 

 sort compelled to exercise it. But these great ques- 

 tions were then more loosely propounded and vaguely 

 pursued. Physical science in those times lent little 

 aid either by facts or methods of enquiry, and induc- 

 tions were drawn from evidence the most incomplete. 

 The condition of the world too is changed. Thoughts 

 and speculations are no longer solitary and exclusive, 

 or limited to particular schools and forms. Know- 

 ledge has become a common heritage, expanded and 

 enriched by free and rapid intercourse over every 

 part of the habitable globe. Nevertheless the dif- 

 ference just denoted is ever present to observation. 

 The physical sciences have rapidly and universally 

 advanced. Metaphysical questions, though better de- 

 fined in their purport, remain unsolved in their ulti- 



