Russel Wallace : Alfred Russell Wallace (sic)
"A Reply to My Critics." (S609: 1903)
But as they express opinions adverse to my conclusions--these conclusions having been reached by a careful survey of the available evidence--and as you seem to think that these opinions show that "the great weight of scientific authority" is against me, I will, with your permission, state briefly why I hold that these expressions of opinion are wholly valueless from the critical or scientific standpoint.
My book is in some degree a protest against deciding a great question of both scientific and popular interest by an appeal to mere weight of opinion, or vague general argument, unsupported by any careful examination of the whole of the facts. I have endeavoured myself to avoid any expression of my own opinions or beliefs as to the subject-matter of my work, considering all such a priori opinions to be wholly worthless; but I have limited myself to stating the conclusions which seem to me to be either the logical inferences from ascertained facts or probabilities from the preponderating weight of the available evidence.
I should welcome any real and thoughtful criticism, even if it should demonstrate important errors in my facts or fallacious reasoning in my conclusions from them, since my only object is to determine whether my conclusions or those of my opponents most nearly approach to the actual truth.
The Complexity of Facts.
Sir Oliver Lodge, while apparently agreeing with my conclusion as to the inhabitability of any other planet of the solar system--a conclusion which, so far as I am aware, no other writer has reached--entirely fails to go further with me. He says: "But to suppose that of all the myriads of solid bodies in space this particular lump of matter is the only one inhabited by intelligent beings seems to me absurd." And he considers the astronomical arguments with which I have supported my view to be "of a futile description."
But the absurdity or reasonableness of such a belief cannot be settled a priori, or even by an appeal to such facts as immensity of numbers or superiority of size. It will depend upon a careful consideration of all the facts which have influenced or rendered possible the whole course of life-development on the only planet on which we know it has developed.
I believe I have shown, for the first time, how very numerous and very complex are these facts, and therefore how enormously improbable it is that an almost identical combination should have occurred elsewhere. I feel sure that in such a first attempt I cannot have exhausted the list of these essential conditions, and each additional fact of this nature enormously increases the improbability I have pointed out.
It must be remembered that this improbability applies also to any hypothetical planet of any other sun than ours, and, even if the astronomical arguments I have adduced against the probability of there being any considerable number of suitable suns may be weak standing alone, they become exceedingly strong when compounded with the improbability of all the requisite planetary conditions simultaneously occurring, and persisting during the enormous periods of time essential for the development of intelligent beings. Such an argument as this is not, I submit, to be disposed of by a mere allegation of absurdity.
The Most Weighty Argument.
My critic then restates Professor Turner's argument, or rather allegation, that our position in regard to the Milky Way makes no difference at all as to the habitability of our planet, and by prefixing the expression "I would urge" he evidently considers it a valid argument. But in the first place the statement is a mere supposition unsupported by any evidence, and although it might perhaps have been permissible in the discussion of my original article, it becomes altogether worthless as against my book, in the last chapter of which I have given reasons, founded upon a paper by Lord Kelvin, showing that a nearly central position is probably the only one where sufficiently stable conditions could be maintained during the enormous periods needed for the entire course of organic evolution. This argument, perhaps the most important and weighty in the whole book, appears to have been entirely overlooked.
The last paragraph of Sir Oliver Lodge's letter deals with a portion of the argument to which I expressly attach little importance.
Mr. H. G. Wells, whose claims for a careful, unbiassed, and enlightening criticism of new books I have just been reading with the respect and admiration such an excellent piece of work deserves, affords, by his letter, a painful illustration of the not uncommon divergence between a man's theory and his practice.
He begins by disclaiming knowledge of any facts on which either belief or denial can be based. If he had stopped there, there would be nothing more to say; but he goes on to ridicule the whole inquiry by introducing "buttons" and "saucepan-lids" in relation to the grandest phenomenon the human mind can contemplate--the form and structure of the starry universe--and, further, goes out of his way to compare a work which, whatever its shortcomings, is founded upon a careful study of the results of modern science with the most trivial speculations of the Middle Ages.
Probabilities and Speculations.
Coming now to the third eminent writer, Sir William Ramsay, I read his first lines with some surprise, since he implies that facts are "wholly lacking" in regard to the subject-matter of my book. Yet he at once goes on to refer to some of the very facts I have made use of, and founds upon them a speculation as to the possibility of animals existing on some of the "legions" of planets "which doubtless exist."
I have never denied such possibilities, but I absolutely deny their value as a foundation for a rational belief. I claim that probabilities, derived from and based upon a careful survey of all the available facts, have a higher claim as trustworthy guides for our conclusions and beliefs than any amount of speculation as to what may possibly exist under unknown or imaginary conditions. The last sentence in Sir W. Ramsay's letter I hardly see the point of, or what he means by the term "such a book." When carefully considered my present work will be found to have exactly the same merits or defects as my other scientific books, which have gained me a reputation as an expounder of the logical results of other men's work perhaps higher than they deserve.
It is, I confess, a disappointment to me that the first two men of science who have noticed my book should have thought proper to express a bald adverse opinion which will doubtless be accepted as conclusive by thousands of readers, and that they should not have deemed it necessary to point out some few of the numerous errors as to facts or fallacies of reasoning which are usually considered needful to justify such a course. In a work having so wide a range of subject-matter there must inevitably be some such oversights, but, as the entire argument is a cumulative one, I venture to think that it will not be seriously impaired.