The Church has been called to form consciences not to replace them' (Pope Francis, 2016 Amoris Laetitia 37). The Catholic tradition teaches that a person is obliged to follow his or her conscience. This teaching takes into account the way in which the individual's desire for what is good, and his or her capacity to reason about what is good and right, and choose freely to do what is morally right, are related to the idea of objective moral truth. Though we frequently talk about conscience as if it were a thing, it is really an abstract construct that is used to talk about how we engage morally with the world. Conscience, literally translated from its Latin root, means with knowledge. At its simplest level then, to act in good conscience, or to follow one's conscience, is to act in way that is in accordance with the knowledge that one has about a particular situation.
In any given moral situation, there is always a morally right answer; there is always a choice that would be the morally right one. There is, in other words, an objective moral truth, the moral truth. But we have to understand all this very carefully, since it is quite possible that there may be two or more objectively good things that we can choose to do, and since we are free beings, making a choice for either would still be morally right. Given the complexity of most moral situations, the challenge is in knowing what that moral truth is. A large number of variables come into play. Among such variables are the kind of person you want to be, the various competing good things that need to be taken into account, the possible harms, the outcomes desired and the outcomes foreseen though not desired, and of course, the circumstances and the consequences that one cannot foresee. Human beings rely on their individual and collective experience (of which law, tradition and divine revelation forms a part) together with their feelings, and their reasoning ability, to work out what that moral truth is in any given situation. Conscience is the means through which we relate to objective moral truth. The exercise of conscience includes the capacity to perceive which values (goods) and harms (evils) are at stake, the process of reasoning about those values and the ways to achieve them together with judgment about which values and which way to achieve these values is is the morally right one. Conscience understood as the desire for good, the aggregated knowledge of experience and reason about what is good, and the judgments made about what is the good and right thing to do) is the individual's relationship to the objective moral truth. Assuming it was possible for you to have perfect knowledge of any given moral situation, then, provided you always chose to act in accordance with that knowledge, your conscience would be aligned with the truth and would always be perfectly good and perfectly right. To have perfect knowledge would be to know everything about all of the factors involved. Such perfect knowledge includes all the facts (scientific and otherwise) of the matter and all of the circumstances and foreseen and unforeseen consequences. Perfect knowledge also assume that one knew perfectly what all the values (goods) were at stake in a given situation and which were the most important values in that situation (e.g. freedom vs security). Having perfect knowledge would also include the most morally relevant parts of the action (who you want to be by doing this, what you do, and what it achieves), which behaviours are always morally bad because they attack the fundamental good of the human person, and the perfectly correct approach to moral reasoning about all of this. Clearly, such perfection can be attributed only to God. We know, from our own experience, that humans can never have perfect knowledge and hence cannot achieve perfect goodness. But, they can come close to it. That is because they are made in the image of God, and thus have been gifted with the capacities of reason and freedom, and are social beings who can learn from each other. When these capacities and our social awareness are correctly combined, we can acquire proper, if limited, knowledge. We can make moral decisions that we believe to be morally right based on that knowledge. In other words, in moral matters, we can only have 'moral' certainty in our judgments. This means we make the judgment about what we ought to do, or avoid doing, without any well-grounded fear that we are wrong or mistaken in that judgment. In this process, the virtue of prudence, namely, the habit of wise judgment is central. We need also to keep in mind that, through our sharing in the divine life, we are helped by the Holy Spirit in our decisions. The gift of wisdom assists us to see, judge and respond as God would. Thus we are called to collaborate with God in our moral life.