From Herbert Spencer1 22 February 1860
22d Feby. 1860
You have wrought a considerable modificn in the views I held— While having the same general conception of the relation of species genera, orders &c as gradually arising by differentiation & divergence like the branches of a tree & while regarding these cumulative modifications as wholly due to the influence of surrounding circumss. I was under the erroneous impression that the sole cause was adaptation to changing conditions of existence brought about by habit, using the phrase conditions of existence in its widest sense as including climate, food, & contact with other organisms (for general statement of this view see Essay pp. 41. 45.)2 But you have convinced me that throughout a great proportion of cases, direct adaptation does not explain the facts, but that they are explained only by adaptation through Natural Selection—
Many (&c) must have been struck with the fact that among all races of organisms the tendency was for the best individs. only to survive & that so the goodness of the race was preserved
I have in Essay on Population &c remarked this as a cause of improvement among mankind—3
But I & every one overlooked the selection of “spontaneous” variations without which I think you have clearly shown that many of the phenomena are insoluble.
You have shown that the doctrine furnishes explanations to phenomena otherwise inexplicable. However the argument may as yet fall short of direct demonstration yet the indirect demonstn. is to me conclusive. I take it to be incredible that so many different kinds of evidence shd coincide in supporting a doctrine that was untrue—
Footnotes
Bibliography
Correspondence: The correspondence of Charles Darwin. Edited by Frederick Burkhardt et al. 29 vols to date. Cambridge: Cambridge University Press. 1985–.
[Spencer, Herbert]. 1852. A theory of population, deduced from the general law of animal fertility. Westminster Review n.s. 1: 468–501.
Summary
CD has caused a great change in HS’s views, in showing how a great proportion of adaptation should be explained by natural selection not direct adaptation to changing conditions. HS had remarked on the survival of the best individuals as a cause of improvement in man, but he "& every one" overlooked selection of spontaneous variation. Believes so many kinds of indirect evidence must add up to a conclusive demonstration of the doctrine.
Letter details
- Letter no.
- DCP-LETT-2706B
- From
- Herbert Spencer
- To
- Charles Robert Darwin
- Source of text
- The University of Edinburgh Centre for Research Collections (Lyell collection Coll-203/A3/5: 107–9)
- Physical description
- CC 3pp inc
Please cite as
Darwin Correspondence Project, “Letter no. 2706B,” accessed on 24 April 2024, https://www.darwinproject.ac.uk/letter/?docId=letters/DCP-LETT-2706B.xml
Also published in The Correspondence of Charles Darwin, vol. 8