THE PHENOMENA OF ORGANIC NATURE 101 



Is no one of our surest convictions which may not be 

 upset, or at any rate modified by a further accession of 

 knowledge. It was because it satisfied these conditions 

 that we accepted the hypothesis as to the disappearance 

 of the tea-pot and spoons in the case I supposed in a 

 previous lecture ; we found that our hypothesis on that 

 subject was tenable and valid, because the supposed cause 

 existed in nature, because it was competent to account 

 for the phenomena, and because no other known cause 

 was competent to account for them ; and it is upon similar 

 grounds that any hypothesis you choose to name is accepted 

 in science as tenable and valid. 



What is Mr. Darwin's hypothesis ? As I apprehend 

 it for I have put it into a shape more convenient for 

 common purposes than I could find verbatim in his book 

 as I apprehend it, I say, it is, that all the phenomena 

 of organic nature, past and present, result from, or are 

 caused by, the inter-action of those properties of organic 

 matter, which we have called ATAVISM and VARIABILITY, 

 with the CONDITIONS OF EXISTENCE ; or, in other words, 

 given the existence of organic matter, its tendency to 

 transmit its properties, and its tendency occasionally to 

 vary ; and, lastly, given the conditions of existence by 

 which organic matter is surrounded that these put 

 together are the causes of the Present and of the Past 

 conditions of ORGANIC NATURE. 



Such is the hypothesis as I understand it. Now let 

 us see how it will stand the various tests which I laid 

 down just now. In the first place, do these supposed 

 causes of the phenomena exist in nature ? Is it the 

 fact that in nature these properties of organic matter 

 atavism and variability and those phenomena which 

 we have called the conditions of existence, is it true that 

 they exist ? Well, of course, if they do not exist, all that 

 I have told you in the last three or four lectures must 

 be incorrect, because I have been attempting to prove 

 that they do exist, and I take it that there is abundant 

 evidence that they do exist ; so far, therefore, the hypo- 

 thesis does not break down. 



But in the next place comes a much more difficult 

 inquiry : Are the causes indicated competent to give 

 rise to the phenomena of organic nature ? I suspect that 

 this is indubitable to a certain extent. It is demonstrable, 

 I think, as I have endeavoured to show you, that they are 



