The object of this book, which is addressed to all cultured men and women, is to set forth the primitive manifestations of love and to throw light on those strange emotional climaxes which I have called "Metaphysical Eroticism." I have taken no account of historical detail, except where it served the purpose of proving, explaining and illustrating my subject. Nor have I hesitated to intermingle psychological motives and motives arising from the growth and spread of civilisation. The inevitable result of a one-sided glimpse at historical facts would have been a history of love, an undertaking for which I lack both ability and inclination. On the other hand, had I written a merely psychological treatise, disregarding the succession of periods, I should have laid myself open to the just reproach of giving rein to my imagination instead of dealing with reality.