PROGRESSION OR SUCCESSION ? 235 



man within the lapse of a few centuries ; and note how 

 impossible it is to predicate of future life-changes where 

 such a power has been superinduced upon the purely phy- 

 sical agencies of nature ! It is true that man's influence 

 has its limit. He may modify, but he cannot create ex- 

 tirpate, but cannot replace may alter the distribution, but 

 cannot change the character of functional performance. 

 Over and above him are the great external conditions of 

 nature, to which he is as subject as the meanest creature he 

 modifies ; but within certain limits he acts as a sub-creator, 

 and this influence must ever be allowed for in all our rea- 

 sonings on the future aspects of vitality. 



[Progression or Succession?] 



There is just one other speculation, and we can scarcely 

 avoid adverting to it. We have traced a progress in the 

 past, we perceive a progress going on around us, and we 

 presume an analogous progress in the future. Whether, 

 then, is this progress part of some great recurring succession, 

 or is it a progression from a beginning we cannot trace to 

 an eternity of which we cannot even imagine'? ^Nature 

 operates in great successions as well as in what appears to 

 our limited observation a great cosmical progression. We 

 note the movement of the silent shadow on the sun-dial, 

 and were our observations limited to the space between 

 morning and mid-day, we might fairly question whether 

 this slowly-progressing shadow went forward and forward 

 for ever, or whether it did not form part of a recurring suc- 

 cession. We watch, and the shadow attains its meridian, 

 falls back, and again commences its progress to-day as it did 

 on the yesterday, and as we presume it will do on the to- 

 morrow. As the earth daily on her axis, so also in her 



