Fruitfulness is the first of a series of four works in which Émile Zola proposes to embody what he considers to be the four cardinal principles of human life. These works spring from the previous series of The Three Cities: Lourdes Rome and Paris which dealt with the principles of Faith Hope and Charity. The last scene in Paris when Marie Pierre Froment's wife takes her boy in her arms and consecrates him so to say to the city of labor and thought furnishes the necessary transition from one series to the other. Fruitfulness says Émile Zola creates the home. Thence springs the city. From the idea of citizenship comes that of the fatherland; and love of country in minds fed by science leads to the conception of a wider and vaster fatherland comprising all the peoples of the earth. Of these three stages in the progress of mankind the fourth still remains to be attained.