The following is a quote from The U.S. Bishop’s Reflection on Catholic Teaching and Political Life:

17. The Church equips its members to address political and social questions by helping them to develop a well-formed conscience. Catholics have a serious and lifelong obligation to form their consciences in accord with human reason and the teaching of the Church. Conscience is not something that allows us to justify doing whatever we want, nor is it a mere “feeling” about what we should or should not do. Rather, conscience is the voice of God resounding in the human heart, revealing the truth to us and calling us to do what is good while shunning what is evil. Conscience always requires serious attempts to make sound moral judgments based on the truths of our faith. As stated in the Catechism of the Catholic Church, “Conscience is a judgment of reason whereby the human person recognizes the moral quality of a concrete act that he is going to perform, is in the process of performing, or has already completed. In all he says and does, man is obliged to follow faithfully what he knows to be just and right” (no. 1778).

18. The formation of conscience includes several elements. First, there is a desire to embrace goodness and truth. For Catholics, this begins with a willingness and openness to seek the truth and what is right by studying Sacred Scripture and the teaching of the Church as contained in the Catechism of the Catholic Church. It is also important to examine the facts and background information about various choices. Finally, prayerful reflection is essential to discern the will of God. Catholics must also understand that if they fail to form their consciences in the light of the truths of the faith and the moral teachings of the Church they can make erroneous judgments…

20. …Catholics may choose different ways to respond to compelling social problems, but we cannot differ on our moral obligation to help build a more just and peaceful world through morally acceptable means, so that the weak and vulnerable are protected and human rights and dignity are defended.

22. There are some things we must never do, as individuals or as a society, because they are always incompatible with love of God and neighbor. Such actions are so deeply flawed that they are always opposed to the authentic good of persons. These are called “intrinsically evil” actions. They must always be rejected and opposed and must never be supported or condoned. A prime example is the intentional taking of innocent human life, as in abortion and euthanasia. In our nation, “abortion and euthanasia have become preeminent threats to human dignity because they directly attack life itself, the most fundamental human good and the condition for all others” (Living the Gospel of Life, no. 5).