79 



would seem, primd facie, to be contradicted in another. 

 It is surely more philosophical to endeavour to reconcile 

 the two, by tracing out (as may frequently be done) 

 some opposing principle in the latter, which shall enable 

 us to understand the discrepancy, and to believe that 

 the same action may be going on in both cases, but that 

 in one of them it is either overruled by a greater con- 

 trolling power than itself, or else has not had sufficient 

 time to bring its fruits to maturity. If a proposition be 

 true, we should recollect that it is always so (under all 

 the circumstances and conditions to which it is appli- 

 cable) ; for, otherwise, it would be both true and false, 

 which is absurd : hence, if my premises be true, that 

 the general tendency of isolation is to diminish the 

 stature of those insects which have become isolated ; it 

 follows that that tendency must remain, so long as there 

 are no other special disturbing influences to absorb or 

 neutralize it. " When any observation/' says a writer 

 of the last century, ' ' hath hitherto constantly held true, 

 or hath most commonly proved to be so, it has by this 

 acquired an established credit : the cause may be pre- 

 sumed to retain its former force ; and the effect may be 

 taken as probable, if in the example before us there doth 

 not appear something particular, some reason for excep- 

 tion*" Hence it is, that, even amongst the opposite 

 phenomena which one island may occasionally present 

 from those of another, I have often been able to recog- 

 nize the working of a selfsame law ; and clearly to detect, 

 * Religion of Nature Delineated, p. 99. 



