These three objections have been urged from time to time by not a few of the most eminent botanists and zoologists of our century; and from one point of view I cannot myself have the smallest doubt that the objections thus advanced are not only valid in themselves, but also by far the most formidable objections which the theory of natural selection has encountered. From another point of view, however, I am equally convinced that they all admit of absolute annihilation. This strong antithesis arises, as I have said, from differences of standpoint, or from differences in the view which we take of the theory of natural selection itself. If we understand this theory to set forth natural selection as the sole cause of organic evolution, then all the above objections to the theory are not merely, as already stated, valid and formidable, but as I will now add, logically insurmountable. On the other hand, if we take theory to consist merely in setting forth natural selection as a factor of organic evolution, even although we believe it to have been the chief factor or principal cause, all the three objections in question necessarily vanish. For in this case, even if it be satisfactorily proved that the theory of natural selection is unable to explain the three classes of facts above mentioned, the theory is not thereby affected: facts of each and all of these classes may be consistently left by the theory to be explained by causes other than natural selection--whether these be so far capable or incapable of hypothetical formulation. Thus it is evident that whether the three objections above named are to be regarded as logically insurmountable by the theory, or as logically non-existent in respect to it, depends simply upon the manner in which the theory itself is stated.