[F]or every type of experiment there is a numerical quantity, depending partly on the chance of the single event succeeding, and partly on the total … - Karl Pearson

It was only the feeling that, at least in one or two aspects of Francis Galton's later life and of his scientific work, I could perhaps put his contributions to human knowledge more adequately than possibly one or another who might take up the task, if I resigned it, and who would hardly grasp the bearing of that long and intimate scientific correspondence between Galton, Weldon and myself, that I persevered in my endeavour to give some account of a life, wherein an important chapter of personal development must remain largely unrecorded.

Now it will, I think, be found that the fields of inquiry where science has not yet penetrated and where the scientist still confesses ignorance, are very like... alchemy astrology and witchcraft... Either they involve facts which are in themselves unreal—conceptions which are self-contradictory and absurd, and therefore incapable of analysis by the scientific or any other method,—or, on the other hand, our ignorance arises from an inadequate classification and a neglect of scientific method.

Preface, pp. xii-xiii. Here Pearson refers to Clausius' Ueber die Verdäderungen welche in den bisher gebräuchlichen Formeln für das Gleichgewicht und die Bewegung elastischer fester Körper durch neuere Beobachtungen nothwendig geworden sind, in Poggendorf's Annalen (1849) Vol. 76, pp. 46-67; and to Weber's Königliche Gesellschafl der Wissenschaflen (1835).