Masculine intellection, pure and simple, is initiative, vigorous, enterprising; analytical, logical, critical; its outlook rational and concrete, its disposition just and honest. Capable in the degree of its virility, of strenuous and sustained endeavour, of keen concentration and close application; taking nothing for granted, but questioning and demanding proof of all things, it is an admirable executive agent of Mind. _Per se_, however, it is rational and deductive, judicial and judicious, rather than inspirational and creative. The blending with it of the Woman-faculty in him quickens his male brain by contributing the emotional element; endues it with intuitive sensibility, fructifies it with female creativeness. Thus it blossoms in Imagination--a new talent, which his natural intellectual energy and executive ability enable him to raise to highest issues in Inductive Science and the creative Arts. Sex, with its phenomena of the characteristics of both sexes blended but, nevertheless, distinctive in the totally dissimilar constitution of members of both, presents an enigma which all the thinkers of all the ages have left unsolved. What is its significance--what its explanation? How has it been possible--without miracle, but by way of biological sequences of form and process, of function and faculty--for the divergent characteristics, physical and mental, of the two sexes to have developed in both, not only without either order of characteristics (normally) neutralising those of the other, but, on the contrary, with both orders ever further intensifying their differences in the sex to which they belong? By hereditary transmission. True! But by what precise means? Because Nature achieves her results always by the continuous operation of unerring Law and intensifying processes, not by eccentricities or deviations. When she seems to us to skip at random, it means that we have missed some intermediate footprints linking her progressive sequences in a long unbroken train. This problem of human duality, physical and psychical, has baffled not biologists only, but philosophers, religionists and seers. It fills both life and literature with puzzles, paradoxes, incongruities. It has been the source of perpetual misapprehension, misconception, maladministration, personal and ethical. It lies at the root of the whole Woman question. It has supplied the motive--and has made the mischief of the Feminist propaganda and practice.