When we thus contemplate the process of social hygiene, we are no longer in danger of looking upon it as an artificial interference with Nature. It is in the Book of Nature, as Campanella put it, that the laws of life and of government are to be read. Or, as Quesnel said two centuries ago, more precisely for our present purpose, "Nature is universal hygiene." All animals are scrupulous in hygiene; the elaboration of hygiene moves _pari passu_ with the rank of a species in intelligence. Even the cockroach, which lives on what we call filth, spends the greater part of its time in the cultivation of personal cleanliness. And all social hygiene, in its fullest sense, is but an increasingly complex and extended method of purification--the purification of the conditions of life by sound legislation, the purification of our own minds by better knowledge, the purification of our hearts by a growing sense of responsibility, the purification of the race itself by an enlightened eugenics, consciously aiding Nature in her manifest effort to embody new ideals of life. It was not Man, but Nature, who realized the daring and splendid idea--risky as it was--of placing the higher anthropoids on their hind limbs and so liberating their fore-limbs in the service of their nimble and aspiring brains. We may humbly follow in the same path, liberating latent forces of life and suppressing those which no longer serve the present ends of life. For, as Shakespeare said, when in _The Winter's Tale_ he set forth a luminous philosophy of social hygiene and applied it to eugenics, "Nature is made better by no mean But Nature makes that mean ... This is an art Which does mend Nature, change it rather, but The art itself is Nature." In whatever way it may be understood, however, social hygiene is now very much to the front of people's minds. The present volume, I wish to make clear, has not been hastily written to meet any real or supposed demand. It has slowly grown during a period of nearly twenty-five years, and it expresses an attitude which is implicit or explicit in the whole of my work. By some readers, doubtless, it will be seen to constitute an extension in various directions of the arguments developed in the larger work on "Sex in Relation to Society," which is the final volume of my _Studies in the Psychology of Sex_. The book I now bring forward may, however, be more properly regarded as a presentation of the wider scheme of social reform out of which the more special sex studies have developed. We are faced to-day by the need for vast and complex changes in social organization. In these changes the welfare of individuals and the welfare of communities are alike concerned. Moreover, they are matters which are not confined to the affairs of this nation or of that nation, but of the whole family of nations participating in the fraternity of modern progress.