By Steven P. White .

I just finished spending two weeks studying the Church's social teaching with a group of young men and women in Krakow, Poland. The students came from all over the world: predominantly the United States and Poland, but also Cameroon, the Philippines, Finland, Hungary, Ukraine, and Slovakia.

One of the biggest challenges in teaching students Catholic social teaching is helping them understand that the Church's social teaching is more than a collection of moral exhortations and prohibitions, though it certainly includes both. As I always emphasize to my students, the Church's social teaching is descriptive before it is prescriptive.

That is, if we want to understand what the Church says about what we owe to one another as persons, or how we ought to order our common life in service to the common good, we must first understand what it means to be a person and what it means to be part of a society, and what the Church means by the common good.

Over the years, the Church has identified what she calls the four "permanent principles" of Catholic social teaching: The dignity of the human person, solidarity, subsidiarity, and the common good. If one understands these principles and how to apply them, then Catholic social teaching becomes a powerful framework for thinking through some of the thorniest problems of contemporary life. Begin with general principles and apply them to the particulars of public life. Sounds simple, right?

Not quite.

Knowing the principles that ought to guide our moral action and applying them is obviously important, but in an age marked by skepticism and relativism, the principles themselves must be accounted for. It is one thing for the Church to speak, for example, of "human dignity" or "natural law," and the faithful may take these as axiomatic simply on the basis of the authority of the Church. It is another thing to be able to defend, justify, and propose the principles to a world that doesn't acknowledge the Church's authority.

Among Catholics, there is sometimes a tendency to treat moral theology - which includes Catholic social teaching - as a sort of moral mathematics, a moral algorithm. Begin with fixed principles, enter certain inputs, and the moral calculus produces concrete moral judgments. The whole process is seen as deductive, deriving certitude in particular judgments on the basis of fixed general principles.

The problem with this is not that it treats certain principles as fixed and true, nor that it treats moral truth as something that we can know, but that relatively few moral decisions can be made on the basis of deductive reasoning alone.

Most of what we learn, we learn through induction: we begin with noticing the way things are and, on the basis of those particulars, we derive general principles. This way of arriving at the truth does not always follow the laws of deductive logic, but it is no less capable of arriving at the truth. For example, it's a formal fallacy of deductive logic to hold that the word of an untrustworthy person ought to be considered untrustworthy. But we all know from experience, that liars aren't to be trusted.

It's reasonable not to trust liars even while acknowledging that the character of one making an argument does not determine the logical validity of the argument he makes. A reasonable person uses both deductive and inductive reasoning because both lead us to the truth. If we rely exclusively on one or the other, we hamstring our own ability to acknowledge the truth.

A great teacher of mine used to say that human beings are "datives of truth," by which he meant that our capacity to receive and recognize the truth is the most distinctive thing about us. It's practically the definition of the human person: We were made for truth.

Understanding the truth about the human person requires us to make use of the full array of human reason, just as understanding the natural law requires us to pay close attention to the nature of things. Unde...