THE ORIGIN OF SPECIES 499 



THE AEGUMENT FOE OEGANIC EVOLUTION" BEFOEE 

 "THE OEIGIN OF SPECIES" 



By Professor ARTHUR O. LOVBJOY 



THE UNIVERSITY OF MISSOURI 

 I 



IN this year of the Darwin centenary it is worth while to raise 

 two questions which have, in the mass of literature elicited by the 

 occasion, received less consideration than they merit. At what date can 

 the evidence in favor of the theory of organic evolution — as distinct 

 from the hypothesis of natural selection — be said to have been fairly 

 complete : in other words, how early were the facts and principles from 

 which the truth of that theory is now ordinarily inferred sufficiently 

 known to all competent men of science, to require the inference, even 

 though it was not, in fact, generally made? And by what English 

 writer was a logically cogent argument for the theory first brought 

 together and put before the public? The interest attaching to these 

 questions is much more than merely historical. The answer to them 

 will afford a sort of object-lesson in the logic of scientific reasoning. 

 Here is a doctrine now accepted by all naturalists: at what point, in 

 the century-long accumulation, through half a dozen separate sciences, 

 of the evidences inclining to that doctrine, ought we to say that the 

 balance of logical probability turned decisively in its favor? The in- 

 quiry will also be found, I think, to throw a somewhat instructive light 

 upon the psychology of belief, and to show how far, even in the minds 

 of acute and professedly unprejudiced men of science, the emotion of 

 conviction may lag behind the presentation of proof. 



By this time, no doubt — though it has not long been so— every 

 schoolboy knows that Darwin did not invent the theory of evolution. 

 The Darwin centenary itself has served to remind the public of the 

 names and works of at least some of the earlier protagonists of the 

 doctrine: of the elder Darwin, namely, of Lamarck, of Geoffroy St. 

 Hilaire, of the author of the "Vestiges of the Natural History of 

 Creation," and of Herbert Spencer. It is less commonly remembered, 

 but perhaps not universally forgotten, that among English-speaking 

 naturalists, the theory was a commonplace topic of discussion for two 

 or three decades before 1859, and especially after the publication and 

 immense circulation of the successive editions of Eobert Chambers's 

 ' Vestiges," of which the first appeared in 1844. Geological text-books 

 of the period referred to the " theory of transmutation of species " as 



