This article presents a current view on fidelity and conjugal love in the light of the fifth chapter of Gaudium et spes, «Fostering the nobility of marriage and the family». It is a document published over fifty years ago, whose cultural context was thus marked by Paul VI's encyclical Humanae vitae as well as by the so-called sexual revolution. This article analyzes the consequences of this revolution and the ruptures that it caused in naturally united and associated areas. Their philosophical and cultural roots are also analyzed. Fidelity is a preserved and augmented freedom. However, it is difficult to practice fidelity in a society where an affective-sentimental conception of love and happiness predominates and where the culture of divorce impregnates the people's mentality. It is certain that marriage is an effect of love, but it is truer still that love is a fruit of marriage. Fidelity is the only thing that goes beyond time and allows love to grow and achieve its fullness.