In the Catholic religion, the Doctrine of Conscience is a set of homilies and precepts that establish a code of moral feeling; that is, the acceptance of how one may feel in certain situations, and what is definable by Catholic beliefs.
There are a great many Doctrines of Conscience applying to various moral and religious codes, but the Catholic version is the one that seems most prevalent. It was probably first codified by St. Augustine of Hippo, and then permeated throughout religion by many others.
In essence, a Doctrine of Conscience intends to show how feelings are permitted throughout life, and how a moral code is the key to happiness. Religion offers one such moral code, showing how God and related philosophy give a set of standards by which to live. The conscience is "feeling" instead of "knowing," and differs in all people, but generally is a method of "gut reaction" giving a sense of right and wrong. By showing what feelings are right and wrong, the religious aspect is strengthened.
Other philosophies all have similar doctrines, each making a statement about feelings and how they are part of everyday life, some of them reconciling religion with science, others showing evolutionary or other meaning to emotions and feelings. Most have this in common: they intend to be a catch-all set of "right thinking," not rights and wrongs (e.g. the Ten Commandments) but instead perceptions and modes of thinking, feeling, and acting.