I have now recapitulated the chief facts and considerations, which have thoroughily convinced me that species have been modified, during a long course of descent, by the preservation or the natural selection of many successive slight favourable variations. I cannot believe that a false theory would explain, as it seems to me that the theory of natural selection does explain, the several large classes of facts above specified. It is no valid objection that science as yet throws no light on the far higher problem of the essence or origin of life. Who can explain what is the essence of attraction of gravity? No one now objects to following out the results consequent on this unknown element of attraction; not-withstanding that Leibnitz formerly accused Newton of introducing “occult qualities & miracles into philosophy.”—

Charles Darwin

p 514 3^d Edit of “Origin”²