Lordship of Christ and the Separation of Church and State by William Einwechter

Explores different views on the relation of church and state, and then discusses the biblical view.  An excerpt:

In Scripture, church and state are treated as separate institutions each having their own clearly defined ministry and sphere of authority. However, both church and state are also presented as being divine institutions and ultimately answerable to God. In Old Testament Israel, church and state were separate institutions within the covenant nation of Israel. Both were commanded by God to serve Him in their appointed sphere. By obeying God's Word, each contributed to the well being of the nation and to the advance of God's kingdom in Israel. Church and state were not competing institutions, nor was one under the authority of the other. Rather, each stood directly under Yahweh who was Lord of both church and state. Hence, the relationship between church and state was defined by their common covenant Head. Church and state in Israel were united by a common allegiance to Yahweh; yet church and state were separate institutions by the will and command of Yahweh.

In the New Testament, the kingdom of God is not limited to one nation. However, the doctrine of Christ's lordship over both church and state means that the basic relationship that existed in Israel between church and state is the relationship that should exist between church and state today. Church and state are to be united by a common allegiance to Jesus Christ, but are to remain separate as institutions.

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