Dear M^r Darwin

By some mysterious process M^r Malcolm Guthrie learnt that I was desirous of reading his book soon after our conversation about it and sent it me.¹ I have not quite finished it but I have read sufficient to enable me to say what I think of it which you so kindly asked me to do.

The book is a very able and acute criticism of First Principles,², written with great fairness and a sincere desire to ascertain the value of what Herbert Spencer has done. Nothing could be more admirable than the patience & attention with which he follows M^r Spencer through the most intricate subtleties of his theories to find out what is his real meaning and the impartial way in which he tests the results at which he arrives. It is a most valuable contribution to the criticism of Spencer’s works for it is likely to impress and hold the more thoughtful portion of those who are so far his disciples as to accept the truth of his physical speculations.

So much for one side of the picture. But there is another side. The Critique & the book criticized are tainted with the same inherent vices. The arguments of the critic are exactly of the same kind as those of the author and are equally open to attack. There is the same fatal habit of patching up our imperfect knowledge of physical truths by evolving fresh ones out of our inner consciousness. There is the same use of vague and scientifically meaningless phrases without any attempt to attach to them any definite signification. There is the same exclusive reliance upon words and verbal formulæ without any consideration of the things they denote. And above all there is the same radical ignorance of the things about which they are disputing. Such phrases as Force, Continuity of Motion, Indestructibility of Matter, Quantum of motion are freely used by both without any accurate knowledge of what they mean.³ Such looseness might have been excusable in the days of Plato or Lucretius, though it would have been none the less fatal to the scientific value of the works. Now-a-days it is both fatal and unpardonable. To put the matter harshly, M^r Guthrie’s book is a pseudo-scientific criticism of a pseudo-scientific work. If either he or M^r Spencer had prepared themselves for their respective tasks by getting a really accurate knowledge of the results of Modern Physics & Dynamics neither First Principles nor the critique upon it could have been written.

But it may fairly be said— Does a purely verbal philosophy deserve any thing better than an equally verbal criticism? The objection to this mode of viewing the case is that if these matters are looked upon as mere efforts in dialectics there is no prospect of deciding the controversy. It is then a mere question of ingenuity to find a reply to any attack and each side can go on alternately being slaughtered & slaughtering to the end of time without being any the worse for it or any nearer the attainment of the truth. It reminds me of a remark that in passing I one day overheard from a spectator of a street fray in which two inexperienced pugilists were making furious demonstrations & flinging their arms wildly about in their efforts to hit each other but were doing little or no execution. In a tone of deepest contempt he ejaculated “A month of this would not hurt ’em. The’re a pair of blooming windmills”. It is just so with these dialectic controversies about scientific matters. They never have settled and never can settle anything. It is clear that both the disputants in the present case think that if our knowledge of physical truths is actually limited and imperfect it can be extended and improved by writing about them. I am happy to say that our present school of Physicists dont agree with them on this point.

I fear that I have wearied you with this unconscionably long letter. But I always find myself roused by any attempt to supplant our only true means of acquiring knowledge—observation & experiment—by the cheap mode of speculation as to what may be and taking those hypotheses which are capable of being most attractively draped in quasi-scientific language as demonstrated truths. And this is from beginning to end the method of Herbert Spencer’s “First Principles”.

I remain | Yours very sincerely | J Fletcher Moulton

C. Darwin Esq F.R.S.