(a) It obliges by reason of divine command, since it acts as the voice or witness of God making known and promulgating. to us the moral law. Hence “all that is not from conscience is sin” (Rom, xiv. 23). (b) Conscience obliges from the nature of things, for, since the will is a blind faculty, it must be guided by the judgment, of the intellect, and must follow the inner light given it about the law. Apart from revelation, there is no other way of learning what God wishes one to do here and now. 581. The authority of conscience is not, however, unlimited. (a) Conscience is not independent of external law and authority. It is not autonomous morality of the reason or will, nor private inspiration or interpretation; for its function is not to establish law or pass judgment on it, but to apply the law as expounded by the Church to a present case. Hence, conscience must aim to be true--that is, to agree with and express the objective law. (b) Conscience is not independent of the righteousness of the will. It is not a speculative judgment, whose value depends solely on agreement between the mind and the facts, as is the case with a conclusion of pure science. It is a practical judgment, which has to guide all man’s conduct, and thus its value depends on the relation of the means it selects to the end towards which the means should be directed. Hence, conscience must be good--that is, a judgment dictated by a will well disposed towards the true end of life. (c) Conscience is not independent of the certainty of the intellect. It is a judgment formed, not by sentiment, emotion, or one’s own wishes, but by evidence and firm conviction; for its office is to guide man reliably in the most important of affairs. Hence, conscience must be certain--that is, a judgment to which the intellect yields its unhesitating assent. 582. In order, therefore, that conscience may be the proper rule and moderator of man’s moral life, it must have the following qualities: (a) It must be good, and practically true--that is, in agreement with the Last End of man and, as far as the efforts of the individual can attain to such agreement, with the objective law--for the standard of moral good is not each one’s wish or opinion, but God as the Last End and the external natural and positive law as means to that End. (b) It must be certain--that is, without fear that one is wrong; at least, it must have that degree of certainty which is possible in moral matters. For to act with the fear that one is committing sin, is to be willing to do what may be sin, and is thus consent to sin.