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” (Catechism #1778).
Conscience is not a little man or woman on your shoulder, or some little voice in your head telling you what to do or not to do. It is a judgment made by your intellect that some action is good and should be done or is evil and should be avoided. Since our judgment is human, it is not perfect. We can make bad judgments even in good faith and with the best of intentions. Knowing that, we are obligated to form a good conscience.
Forming a good conscience involves prayer, study, and dialogue. Prayer is communicating with God. Listening to Him helps form a good conscience. Studying the Bible and the Catechism are also indispensable tools to forming a good and correct conscience. Not only is our judgment imperfect, but so is our knowledge. No one knows everything (except for God).
Therefore, it is crucial to read and study Sacred Scripture (Bible) and Sacred Tradition (Catechism) to have a correct and informed conscience. Talking to good, moral people when we are uncertain or doubtful is also vital to forming a good conscience. Sometimes others can see more clearly and more objectively than we can due to our emotions, personal history, and other factors.
Someone might erroneously think it is morally permissible to steal from the rich to give to the poor. They must follow that conscience only if it is certain and there are no doubts. Furthermore, that person has a moral obligation to form a correct conscience, which means he or she must verify their position and not just claim “I was following my conscience.” They must test their conscience by comparing it to what the Church teaches. In any conflict, the Church’s teachings must prevail since she has 2,000 years of wisdom and grace; we don’t.
The Church also teaches that we should always follow a certain conscience (as long as we do not know or do not suspect it is erroneous), but we should never act on a doubtful conscience. It is also our duty to form a correct conscience that can be tested by comparing our judgment to what is taught in the Bible and in the Catechism.
There is no carte blanche on lax or improperly formed consciences. God will judge us according to our conscience and how well we formed it.