to those who are guided by them. By comparing the current ideas at widely different epochs and under widely different civilizations we are able to ascertain what part of our convictions is really innate and permanent, and what part has been acquired and is transient.
It is above all things needful for the successful progress of Eugenics that its advocates should move discreetly and claim no more efficacy on its behalf than the future will confirm ; otherwise a re-action will be invited. A great deal of investigation is still needed to shew the limit of practical Eugenics, yet enough has been already determined to justify large efforts to instruct the public in an authoritative way, as to the results hitherto obtained by sound reasoning, applied to the undoubted facts of social experience.
My best thanks are due to the Editor of Nature, to the Council of the Sociological Society, and to the Clarendon Press of Oxford, for permission to reprint those among the following essays that first appeared in their Publications.