We might even predict annually how many individuals will stain their hands with the blood of their fellow-men, how many will be forgers, how many wil… - Adolphe Quetelet

Hitherto, the science of Man has been limited to researches... respecting some of its laws, to results deduced from single or insulated observations, and to theories often based on mere glimpses; and these constitute pretty nearly all the materials it possesses.

I would suggest... the idea of a work which should have for its object the analytic examination of the development of our intellectual faculties for each age. Now, I have aimed to present, in the work here reproduced, only an essay, only a particular example, of such an analysis, "which tends to show that the maximum of energy of the passions occurs about the age of twenty-five." The minimum is not then determined; and even when it shall be, by a sufficient number of observations, one will no more be able to apply it to any given individual in particular, than one could make use of a table of mortality to determine the period of his decease.

The progressive development of moral and intellectual man has scarcely occupied their [scientists] attention; nor have they noted how the faculties of his mind are at every age influenced by those of the body, nor how his faculties mutually react.