Ch. i. Wallace. Condorcef. 9 



excess ; from the destruction of the two great 

 causes of the degradation of man, misery and too 

 great riches; from the gradual removal of trans- 

 missible and contagious disorders by the im- 

 provement of physical knowledge, rendered more 

 efficacious by the progress of reason and of social 

 order; he infers, that though man will not abso- 

 lutely become immortal, yet the duration between 

 his birth and natural death will increase without 

 ceasing, will have no assignable term, and may 

 properly be expressed by the word indefinite. 

 He then defines this word to mean either a con- 

 stant approach to an unlimited extent without 

 ever reaching it ; or an increase in the immensity 

 of ages to an extent greater than any assignable 

 quantity. 



But surely the application of this term in either 

 of these senses to the duration of human life is in 

 the highest degree unphilosophical, and totally 

 unwarranted by any appearances in the laws of 

 nature. Variations from different causes are es- 

 sentially distinct from a regular and unretrograde 

 increase. The average duration of human life will, 

 to a certain degree, vary from healthy or unhealthy 

 climates, from wholesome or unwholesome food, 

 from virtuous or vicious manners, and other 

 causes ; but it may be fairly doubted whether 

 there has been really the smallest perceptible ad- 

 vance in the natural duration of human life, since 

 first we had any authentic history of man. The 

 prejudices of all ages have indeed been directly 

 contrary to this supposition ; and though I would 



