134 Dr Alison on the Principle of Vital AJlnity, 



peculiar causes come into play ; and next, to endeavour to 

 obtain some insight into the peculiar character and attributes 

 of these causes."* 



When we say that the chemical changes which take place 

 in living bodies are elucidated, we mean, of course, that they 

 are referred to general laws, by which the phenomena ob- 

 served in this department of Nature are found, by experi- 

 ence, to be regulated. And when we say that these are laws 

 of vitality or of vital action, we mean merely, that they are 

 laws deduced from the observation of phenomena peculiar to 

 the state of life, — taking for granted that it is always pos- 

 sible to describe, and practically to distinguish, those sub- 

 stances which we call living, from inorganic or dead matter ; 

 and that the only correct definition of vital principles or vital 

 powers, is, that they are the laws or the powers which regu- 

 late the phenomena that are peculiar to the state of life. 

 They are the general expression of the results of the obser- 

 vation, and generalization of the facts, which are observed in 

 this department of nature, and which are ascertained to be- 

 long to this department alone. 



We are not, indeed, justified in asserting the existence of 

 laws peculiar to the state of life, merely by the negative ob- 

 servation, that the phenomena referred to them are inexpli- 

 cable by any known laws of inorganic or dead matter ; we 

 must have the positive observation that they are inconsistent 

 with — that they take place in despite of — the laws which re- 

 gulate the changes of dead matter. It is thus that we are 

 led to ascribe the visible movements of living bodies to vital 

 powers ; not because we do not perceive how gravitation, 

 elasticity, or any other known causes of movement in dead 

 matter, should produce them, but because we do perceive, 

 that, in the circumstances in which we see these motions, all 

 those principles, deduced from the observation of dead mat- 

 ter, would determine either rest, or motion in a different di- 

 rection from that which really takes place. 



I formerly laid before this Society the grounds of an opinion, 

 then much disputed, but now, I think, pretty generally ad- 



* Philosophy of the Inductive Sciences, vol. ii., pp. 39 and 47. 



