WCP5635

[1] [p. 78]

TO SIR FRANCIS DARWIN

Parkstone, Dorset.

July 3, 1901.

Dear Mr. Darwin,—

Thanks for the letter returned. I do hold the opinion expressed in the last sentence of the article you refer to, and have reprinted it in my volume of Studies, etc. But the stress must be laid on the word proof. I intended it to enforce the somewhat similar opinion of your father, in the "Origin" (p. 424, 6th Edit.), where he says, "Analogy may be a deceitful guide." But I really do not go so far as he did. For he maintained that there was not any proof that the several great classes or kingdoms were descended from common ancestors.

I maintain, on the contrary, that all without exception are now proved to have originated by "descend with modification," but that there is no proof, and no necessity, that the very same causes which have been sufficient to produce all the species of a genus or Order were those which initiated and developed the greater differences. At the same time I do not say they were not sufficient. I merely urge that there is a difference between proof and probability.—

Yours very truly,

ALFRED R. WALLACE.