How can Christians make arguments that are persuasive to those who do not share their most basic presuppositions? That is the quandary in which Christians—and Jews and Muslims—find themselves as public discourse is increasingly framed, mediated, and policed by people for whom religion is not simply incredible, but irrelevant. This dilemma is not new, but it has sharpened significantly as Christians struggle to articulate reasons for supporting marriage as the union of man and woman to a secular culture that suddenly discovered it had no reasonable grounds to agree with them anymore.

The traditional Christian response, and one that some thinkers have tried in recent years, is to frame arguments in terms of natural law. The effort, on the surface, made sense. Because we understand the Gospel of Jesus Christ to be objectively true and applicable to all persons regardless of time or culture, the moral guidelines to which it gives rise are similarly objective and universal. This is natural law: a universal moral code inscribed in creation, applicable across time and culture, and accessible by reason. Because God has written the natural law on the hearts of all mankind, all people—Christian and non-Christian alike—can discern it (though, of course, not perfectly, and not without training and education). Natural law and reason should be a common language with which to talk to others who do not share our belief in revelation.

But Christians have not exhausted the resources available for speaking in terms intelligible, legitimate, and persuasive to those outside the community of faith. There is another such a way. It’s called social science.

Social science is the application of human reason to study the stuff of human life. Social science attempts to describe, explain, and predict human phenomena by using the tools of the scientific method: observation of empirical data based, when possible, on repeatable experiments to test falsifiable hypotheses. Social science as a whole is comprised of subfields, each looking at different aspects of human phenomena: at individuals (psychology), societies (sociology), politics (political science), culture (anthropology), or the production and exchange of goods, services, and labor (economics).

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As the most systematic and rigorous application of human reason to human phenomena, social science is the tool par excellence for investigating the claims of natural law. If Christian ethics and natural law are true, their superiority should be empirically demonstrable through social science. Christian scholars should, in principle, be capable of carrying out a research program describing the social and psychological results of ethical and unethical living and demonstrating Christian ethics’ greater contribution to human flourishing compared to rival moral systems. And scholars should be able to do so without explicit reference to revelation, doctrine, or nature. If we think natural law says, for example, that divorce is bad (reflecting what we know from revelation and can infer from nature), then social science should be able to identify the destructive consequences of divorce by studying the data of actual cases of divorce, explain how and why it is bad, and predict the consequences of continued high divorce rates versus lower divorce rates.

One immediate objection to this approach is that social science is supposed to be morally neutral. Following the scientific method, it should only be concerned with describing the world, not prescribing how to behave in it. Science addresses the “is”: only philosophy and theology can address the “ought,” and we cannot obtain the latter from the former.

If it were true that social science is uncommitted to normative frameworks, this would be a powerful critique. But the neutrality of social science is far less substantial than advertised. As Leo Strauss argued in Natural Right and History, it is impossible, in practice, to provide a morally neutral description of certain kinds of phenomena, such as genocide. Even to describe them is, to a morally sensitive audience, to condemn them.

Such morally informed social science research is borne out in practice. Although social scientists would not readily admit it, most of their research is carried out with an at least implicit goal or telos in mind. In psychology, for example, the telos is a “well-adjusted” individual. Psychologists disagree over what constitutes “adjustment,” but much of the work of psychology is devoted to describing ways in which people are maladjusted, explaining why and how they became so, and prescribing ways of becoming more well-adjusted. The telos of being well-adjusted is a fundamental presupposition that informs, frames, and structures the entire discipline. Although some psychologists have devoted their careers to arguing for the normalcy of behavior that, a generation ago, was considered disordered, they have not mounted an assault on the very notion of normalcy. The American Psychological Association famously removed homosexuality from its list of mental disorders in 1973, but it didn’t abolish the list altogether. It continues to keep a list of mental disorders and thus acknowledges that there are more well-ordered and less well-ordered variations of mental life.

The pattern holds true, to various degrees, through much of the social sciences. In fact, we might be able to judge the health of a discipline by seeing how clearly it retains some sense of telos to guide its research programs. In economics, the telos is prosperity, productivity, and employment. In international relations, the telos is some blend of peace, security, and justice. In political science, the telos should be justice, but, in reality, it has often become victory: political science has become the handmaiden of lobbyists and campaign strategists. Anthropology may be worst off of all. Ideally, it would aim at fostering understanding and enjoyment of cultural pluralism; in reality, it has often aimed at promoting philosophical relativism.

There is, I think, a central organizing concept that can and should provide the telos for all social science: human flourishing. As philosopher Martha Nussbaum has argued in her work, human flourishing should be the universal standard by which to judge the superiority of some ways of living over others. Choices that promote human flourishing are demonstrably superior to those that do not, and it does not require an explicit appeal to revelation to make that claim.

Human life is not infinitely malleable. Not even the most hardened secular liberal will claim, for example, that illiteracy is better than literacy, war better than peace, or poverty than prosperity. There are certain aspects of humanity that we recognize as intrinsically important to humanness across cultures—laughter, sex, abstract thought, family, physical health and wholeness, etc.—without which we would rightly say a life is less than it potentially could be (not worth less, but less fulfilled or realized). Human flourishing is the fulfillment of humanity in all its dimensions. Some choices—basic education, for example—are universally good because they help realize human potential, no matter what culture one lives in. With the normative framework provided by the telos of human flourishing, social science can serve as the common language with which to talk about human life in a way that is comprehensible and legitimate to non-Christians.

This way of demonstrating the truth of Christian ethics and natural law has several advantages. It speaks to non-Christians in a language they claim to accept. It holds itself accountable to the highest standards of intellectual rigor. It tests itself. It speaks dispassionately and objectively, never in the tones of partisanship, intolerance, rote assertion, or the ad hominem. It does not assume that our current understanding of the universal moral law is correct or that our culture’s way of applying it is appropriate in all times and places. It can help the Church correct her understanding of the moral law when it becomes too captive of the prejudices of one time, place, or culture. And social science can speak in more nuanced ways. We might find, for example, that divorce is more damaging in some cases or under certain circumstances than others, and thus enable ourselves to speak more sensitively in a complex world.

What I am suggesting has already been taken up by most actors in public discourse. The best way to make a quotable point in today’s media environment is to cite an expert or a study. Studies provide facts and analysis. If you cite studies, you’re borrowing their intellectual authority and epistemological validity. If you disagree with them, you risk looking as though you’re against science and anti-intellectual. The problems with this are obvious. It provides incentives for biased social science. And it legitimizes all social science, regardless of the telos at which it aims (much, for example, aims narrowly at the telos of personal autonomy rather than human flourishing).

Nonetheless, the use of social science in public discourse is sound in principle. Social science can provide the common language for an ideologically diverse people to talk together about the things of human life. Done rightly and guided by the telos of human flourishing, social science is impartial and objective and thus should be legitimate and persuasive to people of diverse philosophical commitments. Such studies must be undertaken with care and under the highest standards of scholarship lest they give ammunition to critics. But Christians have nothing to fear and everything to gain from good social science, because it should confirm what we already know from natural law—or help us revise our understanding of the natural law in light of human experience.