The complex array of today’s problems branches out from here, including some never faced by past generations. Scientific progress has resulted in advances that are unsettling for the consciences of men and women and call for solutions that respect ethical principles in a coherent and fundamental way. At the same time, legislative proposals are put forward which, heedless of the consequences for the existence and future of human beings with regard to the formation of culture and social behavior, attack the very inviolability of human life. Catholics, in this difficult situation, have the right and the duty to recall society to a deeper understanding of human life and to the responsibility of everyone in this regard. John Paul II, continuing the constant teaching of the Church, has reiterated many times that those who are directly involved in lawmaking bodies have a grave and clear obligation to oppose any law that attacks human life. For them, as for every Catholic, it is impossible to promote such laws or to vote for them. As John Paul II has taught in his Encyclical Letter Evangelium vitae regarding the situation in which it is not possible to overturn or completely repeal a law allowing abortion which is already in force or coming up for a vote, «an elected official, whose absolute personal opposition to procured abortion was well known, could licitly support proposals aimed at limiting the harm done by such a law and at lessening its negative consequences at the level of general opinion and public morality.
In this context, it must be noted also that a well-formed Christian conscience does not permit one to vote for a political program or an individual law which contradicts the fundamental contents of faith and morals. The Christian faith is an integral unity, and thus it is incoherent to isolate some particular element to the detriment of the whole of Catholic doctrine. A political commitment to a single isolated aspect of the Church’s social doctrine does not exhaust one’s responsibility towards the common good. Nor can a Catholic think of delegating his Christian responsibility to others; rather, the Gospel of Jesus Christ gives him this task, so that the truth about man and the world might be proclaimed and put into action.
When political activity comes up against moral principles that do not admit of exception, compromise or derogation, the Catholic commitment becomes more evident and laden with responsibility. In the face of fundamental and inalienable ethical demands, Christians must recognize that what is at stake is the essence of the moral law, which concerns the integral good of the human person. — from Participation of Catholics in Political Life (2002)