Humanae Vitae §3

³ This new state of things gives rise to new questions. Granted the conditions of life today and taking into account the relevance of married love to the harmony and mutual fidelity of husband and wife, would it not be right to review the moral norms in force till now, especially when it is felt that these can be observed only with the gravest difficulty, sometimes only by heroic effort? Moreover, if one were to apply here the so called principle of totality, could it not be accepted that the intention to have a less prolific but more rationally planned family might transform an action which renders natural processes infertile into a licit and provident control of birth? Could it not be admitted, in other words, that procreative finality applies to the totality of married life rather than to each single act? A further question is whether, because people are more conscious today of their responsibilities, the time has not come when the transmission of life should be regulated by their intelligence and will rather than through the specific rhythms of their own bodies.