There are those on both the left and right who are fairly confident that they know what God thinks about politics. And in the months to come, as the race for the presidency heats up, God will be enlisted on both ends of the spectrum to endorse a candidate or two. That's remarkable certainty, given the difficulties associated with applying Scripture to any dimension of the contemporary political landscape.

The Old Testament was addressed to a small federation of tribes who could do little more than react to the foreign policy of their neighbors. Israel was, at once, indistinguishably religious and political. Moreover, it was ruled by a king who—if Scripture is to be taken at its word—was a poor substitute for being ruled directly by God.

The New Testament poses a different set of challenges: Jesus addressed his preaching to a nation that no longer controlled its own political destiny at all, but was forced to wrangle what freedoms it could from its Roman overlords. He seems to have accepted that state of affairs as an intractable reality and urged his readers to distinguish between their obligations to God and the inescapable demands of the Roman Empire. The rest of the New Testament is addressed largely to the shape of the fledgling church itself, which (for much of the period the New Testament covers) was a sect within a sect and lacked any kind of political voice at all.

For that reason the New Testament often urges social behavior that responds to the voice of God in ways that transformed the behavior of Christians living and working within the social institutions of the first century. But, understandably, the writers of the New Testament do not urge the church to craft or change the policy of ancient Rome.

In both Testaments, the institutions within which ancient Jews and early Christians lived were also very different from the ones within which we live today. The ancient world was populated by kings, empires, tribes, and theocracies. It knew nothing of the modern nation-state. Notions of democracy and republics bore little resemblance to their contemporary counterparts and, for the most part, were localized efforts that did not endure. The economic systems of the ancient world were also markedly different from the ones with which we live today. More often than not, they relied on bartering and the market-based exchange of goods. (There were no banks, for example.)

To further complicate matters, when Scripture does talk about social phenomena using language that is familiar to us, it often refers to realities that were very different from their modern counterparts. So, for example, the "poor" in the ancient world were not "poor" because they belonged to a particular socio-economic rung in the ladder, but because they lacked a male (a husband or father) with whom they could be identified. And, at other points (as in some of the Psalms), the plea that God not forget the poor, is the appeal of a nation that was afraid that God would leave them fatherless and unprotected.

Now, none of the complexities associated with reading Scripture means that Christians are not obliged to make faithful decisions about how to live in the world. Nor do the complexities free us from the obligation to vote or evaluate specific political debates. In fact, Christians of the 21st century are called upon to make a wide variety of decisions that lack an ancient, unequivocal precedent, including (for example) decisions about the end of life, birth control, and abortion.