DEFINITIONS OF LIFE. 39 



only in our minds, ut quorum esse est percipi. For if the 

 definite quantities have a ground, and therefore a reality, 

 in the external world, and independent of the mind that 

 perceives them, this ground is ipso facto a quality ; the 

 very etymon of this wor/3. showing that a quality, not 

 taken in its own nature but in relation to another thing, 

 is to be defined causa sufficients, entia, de quibus loquimur; 

 esse talia, qualia sunt. Either the quantities perceived 

 exist only in the perception, or they have likewise a real 

 existence. In the former case, the quality (the word is 

 here used in an active sense) that determines them be- 

 longs to Life, per ipsam hypothesin ; and in the other case, 

 since by the agreement of all parties Life may exist in 

 other forms than those of consciousness, or even of sensi- 

 bility, the onus probandi falls on those who assert of any 

 quality that it is not Life. For the analogy of all that we 

 know is clearly in favour of the contrary supposition, and 

 if a man would analyse the meaning of his own words, and 

 carefully distinguish his perceptions and sensations from 

 the external cause exciting them, and at the same time 

 from the quantity or superficies under which that cause is 

 acting, he would instantly find himself, if we mistake not, 

 involuntarily identifying the ideas of Quality and Life. 

 Life, it is admitted on all hands, does not necessarily imply 

 consciousness or sensibility ; and we, for our parts, cannot 

 see that the irritability which metals manifest to galvanism, 

 can be more remote from that which may be supposed to 

 exist in the tribe of lichens, or in the helvellse, pezizee, &c., 

 than the latter is from the phenomena of excitability in 

 the human body, whatever name it may be called by, or in 



