“(1) The advantageous differences making for survival are not of one kind in any particular case, but of an indefinitely large number (_e.g._, climate getting colder needs not only warmer coat, but power to digest new food, protective colouring so as not to show dark against snow, etc., an indefinitely large number of qualities). Now the chance of _all_ being combined (and co-ordinated) in a single individual, _without design_, _accidentally_, let alone of their thus appearing in many individuals _accidentally and without design_, approximates to zero.” This is, so to speak, the short uncompleted form of the first argument. It is expanded later to a copiousness too great to admit of quotation. This expansion carries the statement right to its conclusion, that only an individual possessing all the possible differences that are advantageous at any particular time can survive. Otherwise its differences have no “survival value.” They may be advantages, but not sufficient advantages to score an advantage. I know this sounds tipsy, but there it is in black and white in Mr. Belloc’s wonderful Article V for any one to consult. It follows plainly that, except for a miracle, every species must be exterminated in every generation. I can see no other way out of it. No individual, he declares, can survive without the full set of advantageous differences, and the chance of any individual having the full set of advantageous differences, he declares after some abstruse verbal gestures, is zero. There is Mr. Belloc with his unfailing logic, his clear mathematical demonstration, and all the rest of it. There is the lucid Latin mind shining above my Nordic fog! Yet the previous generation got along without any of the set! And species do survive. Did Mr. Belloc imagine he was saying something else? It is not for me to speculate. Helping out an antagonist in a controversy is apt to be resented. He has, I think, simply got into a muddle here, and he is not sufficiently self-critical to get out of it again. So he tries to muddle through. It is quite reasonable to say that when a species is under stress of changing conditions it is usual for the need for adaptation to be felt upon a number of points and not simply upon one, and that, since every advantage counts, the individuals with the greatest combination of advantageous differences have the best chances. But that does not alter the fact that even a single advantage is an advantage. What happens in nature is not an extermination of all who are not completely in the fashion of the new differences. That seems to be Mr. Belloc’s idea, but it is a wrong idea. What does happen is a diminution in each generation of the number of the disadvantaged in relation to the number of the advantaged. That is quite another affair. Mr. Belloc has not grasped this. His third _a priori_ argument shows as much even more plainly than his first, and to that I shall presently come.