Over at Public Discourse, Sherif Girgis attempts to field some objections to natural law arguments offered recently in the context of the gay marriage debates. I’m still waiting to hear the political argument against gay marriage from those who reject natural law reasoning, but Mr. Girgis does a good job of explaining some of the basic points of natural law reasoning, namely that some moral knowledge precedes special revelation and works to interpret and evaluate that special revelation. If this were not the case, we would have no way to compare the morality of competing religions, as all such questions would reduce to appeals to authority and circular reasoning: it is moral because this religion is correct. As simple as this answer is, and therefore to a degree satisfying, if applied consistently it would reduce to simple fideism. Politically speaking, at least in the modern spectrum, this position must lead to a sort of religious relativism with the state playing the part of referee or judge. All religions are equally right or equally wrong (take your pick) until they cross certain politically-established lines.
Mr. Girgis also explains that natural law reasoning- or really just the use of philosophy in general- allows us to identify basic principles and apply them in new and creative ways:
Philosophy does not just fill gaps in our understanding of faith without ever touching down to its own philosophical foundations. No, to apply a commandment to new cases, we need to know its rationale. On that, revelation might be silent. And then we will require bedrock appeal to reason… Likewise, for a casuistry of, say, homicide, we need to know why killing is wrong when it is. And it is philosophy, not just revelation, that will show us the relevance of lethal intentions, or of fairness in accepting collateral damage. We therefore need reasoning that is philosophical all the way down, to keep faithful to moral theology.
Another important presupposition here, and one which places the Protestant faith in a stronger position, is that this is all true of individuals. The goal is not to submit to a group of experts, whether professorial, political, or clerical, to be able to think in this way, though this can help in formation. The goal is for all people to be able to understand. This persuasive power of reason thus creates a free society which can still have objective and unchanging truth claims.
Of course this won’t happen perfectly, nor quickly. But it can be cumulatively approached through the cultivation of the mind, the will, and the spirit. This means an education in faith, reason, and morals. These things are united, and yet they avoid totalitarianism precisely because of their belief in reason and persuasion. To win the field by force would be to lose the point being argued.