This view of conscience, I know, is very different from that ordinarily taken of it, both by the science and literature, and by the public opinion, of this day. It is founded on the doctrine that conscience is the voice of God, whereas it is fashionable on all hands now to consider it in one way or another a creation of man. Of course, there are great and broad exceptions to this statement. It is not true of many or most religious bodies of men; especially not of their teachers and ministers.
When Anglicans, Wesleyans, the various Presbyterian sects in Scotland, and other denominations among us, speak of conscience, they mean what we mean, the voice of God in the nature and heart of man, as distinct from the voice of Revelation. They speak of a principle planted within us, before we have had any training, although training and experience are necessary for its strength, growth, and due formation. They consider it a constituent element of the mind, as our perception of other ideas may be, as our powers of reasoning, as our sense of order and the beautiful, and our other intellectual endowments. They consider it, as Catholics consider it, to be the internal witness of both the existence and the law of God. They think it holds of God, and not of man, as an Angel walking on the earth would be no citizen or dependent of the Civil Power. They would not allow, any more than we do, that it could be resolved into any combination of principles in our nature, more elementary than itself; nay, though it may be called, and is, a law of the mind, they would not grant that it was nothing more; I mean, that it was not a dictate, nor conveyed the notion of responsibility, of duty, of a threat and a promise, with a vividness which discriminated it from all other constituents of our nature.
This, at least, is how I read the doctrine of Protestants as well as of Catholics. The rule and measure of duty is not utility, nor expedience, nor the happiness of the greatest number, nor State convenience, nor fitness, order, and the pulchrum. Conscience is not a long-sighted selfishness, nor a desire to be consistent with oneself; but it is a messenger from Him, who, both in nature and in grace, speaks to us behind a veil, and teaches and rules us by His representatives. Conscience is the aboriginal Vicar of Christ, a prophet in its informations, a monarch in its peremptoriness, a priest in its blessings and anathemas, and, even though the eternal priesthood throughout the Church could cease to be, in it the sacerdotal principle would remain and would have a sway.