An important theme of Old Testament history is the way in which God’s people Israel related to the other nations surrounding them. The people of the covenant were not to follow the idolatrous practices of those nations. Israel, after all, had the benefit of God’s revealed law. The other nations did not.
One thing that the Israelites wanted to imitate, however, was the fact that other nations had a king. At one point they demanded of Samuel the prophet, "Give us a king!" Upon consulting the Lord, Samuel was told, "They have asked for a king---Give them a king." But God also gave this essential warning: both the people and their king have a king in heaven! The well-being of the entire nation depends on the obedience which both the king and his people give to the King of heaven. (See 1 Samuel 8:1-22 and 12:13-15.)
The Lord Jesus expressed the same theme in Matthew 22: 15-22. When asked whether taxes should be paid to Caesar, Jesus asked whose image and inscription was on the coin. "Caesar’s," came the answer. The Lord then said, "Then give to Caesar what belongs to Caesar and to God what belongs to God" (Mt. 22:21).
The coin belongs to Caesar, for it bears Caesar’s image. Human beings belong to God, for they bear God’s image! The implication of the passage is that "What belongs to God" includes Caesar himself! Caesar must obey God.
Both the passage from 1Samuel and from Matthew’s Gospel teach what the Second Vatican Council commented upon at length, namely, that separation of Church and state does not mean separation of God and state. If you separate the state from God, the State disintegrates. While the Church does not have a political mission, she nevertheless has a political responsibility: to bear witness to those moral truths without which the common good---which is the very purpose for which governments are instituted---cannot survive. These moral truths are basic and go beyond the bounds of any denominational beliefs. Because they are truths, they must shape public policy.
Not only do individuals have a duty to obey God, but so do governments.
Christians have a duty to be politically active, to register and vote, to lobby and educate candidates and elected officials, and to speak up about the issues that affect the common good. The Church does not set up the voting booths, but when we go into the voting booths, we don’t cease to be members of the Church! If we don’t shape public policy according to moral truths, why do we believe that moral truth at all?
Now is the time, now is the challenge. No longer are we to think of our religion as a purely "private matter." Christ taught in public and He was crucified in public. Now risen from the dead, He places us in the public arena, with the commission to make disciples of all nations (See Mt. 28:18-20). May we not fail Him or our nation.