ESSAY-REVIEWS 97 



law of thermodynamics, there is a universal and unceasing 

 tendency towards the degradation of energy in the form of 

 dissipated heat. The universe, as we see it, is passing from 

 a state in which energy is concentrated at certain places at high 

 potential, to a state in which all the energy will have become 

 dissipated equally everywhere ; and the universe will then be a 

 dead, inert, motionless existence, possessing a uniform tem- 

 perature, representing the degraded sum-total of all the various 

 forms of energy previously concentrated in particular regions. 

 But the universe has existed throughout infinite time : therefore 

 the state of final equilibrium must already have been reached, 

 unless there were somewhere a source of " restoration of avail- 

 able energy " — that is to say, a phenomenon which reverses the 

 degradation of energy, and sets up contrary processes leading 

 once more to concentration at high potential. And we are then 

 introduced to the suggestion (already made by Dr. Johnstone 

 in his Philosophy of Biology) that Life is the source of this 

 reversal of physical processes. 



Now 1 propose, in the first place, to deny that we are called 

 upon to believe in any such reversal of the second law of 

 thermodynamics ; and in the second place to deny that, if there 

 were any such reversal, it could have any possible connection 

 with Life. Had I more space available, I should have begun 

 by criticising Dr. Johnstone's statement of the law itself, which 

 appears to me imperfect in certain particulars. But in order 

 to limit the discussion to the truly essential points, I am pre- 

 pared to accept his statement of the law as true and accurate. 



I may begin then by pointing out that the whole argument 

 is purely deductive in character. Energy is continually being 

 degraded : the past duration of the universe is infinite : there- 

 fore, unless there be some source of restoration, the degradation 

 must long ago have been complete ; but it is far from complete : 

 hence there must be some source of restoration. Now we may 

 gravely doubt the value of any chain of deduction which leads 

 you by two or three simple steps from the infinity of time to 

 a theory of vitalism. The infinity of time is too vague, too 

 metaphysical, and too incomprehensible a doctrine to be suit- 

 able for use as a major premise for the deduction of physical 

 and biological facts. It may, indeed, be questioned whether any 

 deduction should suffice to convince us of the reversibility of 

 a law of thermodynamics, which is based (like the law of con- 

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