As I was trying to write about Christian freedom for the book I'm working on, I began to get that slippery/fuzzy feeling in my head, that something wasn't quite right. Often this feeling comes when I am conflating ideas. And in this case I think I was.
Christian liberty in the Bible: free from human rules, answerable only to God
You see, in the Bible, and confessions like the Westminster Confession of Faith, Christian “liberty of conscience” is about our freedom from human rules and doctrines. Our consciences should not be bound by false religion, or extra-biblical scruples and traditions, because we are ultimately only answerable to God.
This concept of liberty of conscience does not uphold the freedom of men or women to believe in a false religion, nor in their freedom to hold unbiblical positions on moral issues. Our consciences are NOT free from God's word.
But when we speak about 'liberty of conscience' in political science, we mean a slightly different thing.
Liberty of conscience in politics: freedom from human coercion in matters of religion and morality
This idea is about stopping secular governments from over-reaching. They should not legislate too much in matters of morals and religion, so that individual liberty of conscience is preserved. This concept argues for allowing diversity in church demoninations, and diversity in religious beliefs and even diversity in moral opinion. We must allow people to act and worship according to their own conscience.
A version of this might even apply in a church setting. For example, the Presbyterian Church of Australia's 'Declaratory Statement', that is appended to the Westminster Confession of Faith says “That liberty of opinion is allowed on matters in the subordinate standard not essential to the doctrine therein taught, the Church guarding against the abuse of this liberty to the injury of its unity and peace”.
How does New Testament Christian liberty related to liberty of opinion?
I don't make this observation in order to argue that the second kind of liberty is extra-biblical and so unbiblical. In the first place I just want to conceptually separate them, so that you and I can think and speak more clearly.
I actually think the two work well together. I think the teaching about Christian liberty in the New Testament points in a way that encourages to allow a certain degree of liberty of opinion in the church and especially in society as a whole. Romans 14 strongly argues that people are ultimately responsible to God, not to human authorities (including church leaders). The same chapter also stresses that we are each individually responsible to God for our personal beliefs and actions. It is not enough for us just to conform to external powers, whether in the church or in the world: anything that does not come from faith is sin.
A wise church leadership or civil government will consider where and how to allow freedom on points of disagreement regarding religion and morals. To leave room for individual responsibility and the ultimate lordship of God, it is good and right to restrain the reach of human authorities, even if they not adding to God's word, but only seeking to enforce it, as they understand it. So we should give a wide space around individual beliefs and moral action, to support genuine conversion and sincere moral action.
A final reason for supporting the second kind of 'liberty of conscience' is the truth of human fallibility and sinfulness. We human leaders are likely to be wrong when it comes to morality and religion, from time to time! If we are aware of this risk, then we will have an extra, biblical reason to be guarded in how narrowly we presume to legislate beliefs and behaviour.