Sex is a direction. Two is a part of one, growing out of one. As the conductor guides the music, each movement of his baton demands a second movement; a single motion is not possible. A single stroke has no meaning; but as soon as there is a second motion, then the rhythm of the music begins and wins even the hearts of children. In the same way every single expression of activity reveals two aspects or directions of the same action; and these may be distinguished from each other as its positive and negative aspects.