By Thomas J. Lee

What is the right thing to do?

How do you know?

More broadly, how should people tell right from wrong?

Moral philosophers—scholars, lawmakers, novelists and essayists, the judiciary, monks and rabbis—have wrestled with these vital questions for thousands of years. It’s arguable how far they’ve got. For most of us—well, we just think we know. But do we really? And if so, how?

Maybe there is no single correct answer. After all, if it were easy, we would have much more rectitude and many fewer differences of opinion. We would have fewer lawsuits, fewer wars, fewer scandals, fewer fistfights, and many fewer Facebook arguments. We might even get along.

Now, as it happens, I have been thinking about those numbing questions because I am preparing for a discussion next week on moral philosophy for a Great Books reading group. We are reading Utilitarianism, the famous philosophical tract by John Stuart Mill, a British political economist and philosopher who lived from 1806 to 1873. The last time I read it, I was in high school. That was a long time ago, and I needed a refresher course.

It turns out there are three main schools of thought in moral philosophy: virtues, principles, and consequences. It’s a big help to understand all three, so as to have a little braintrust for ethical choices.

The first school of thought, centering on virtue or character, dates back to Aristotle’s great work, Nicomachean Ethics, named for Aristotle’s son, who edited it. This famous tract implores us to be the best persons we can be, by adopting the highest ideals of personal responsibility. It puts a premium on such moral cornerstones as thrift, courtesy, fairness, respect, honesty, civility, lawfulness, and so forth—the kinds of things your mom and dad urged on you when you were a kid.

It sounds straightforward, but it isn’t. All those grand virtues can vary from culture to culture and from era to era. Adolf Eichmann, the Nazi mastermind behind the Holocaust, infamously claimed at trial that he was virtuous, because German culture had long prized fealty to authority, and he was “just following orders.” He was convicted and executed for war crimes, of course, but not before the American journalist Hannah Arendt memorialized his defense as “the banality of evil.” Can anything be virtuous if seen in its own light? It’s a scary thought, but even Stalin, Hitler, and Mao had their apologists.

The second school of thought, centering on principles, pounds its stake deeper in the ground, so it is less yielding to the vicissitudes of time and place. It is simpler, too, if unbending. It dates back to Immanuel Kant, the great German philosopher who lived from 1724 to 1804.

Kant believed that people should live according to certain timeless principles or truths, which are always valid and always governing. He called them “categorical imperatives.” Thus, he asserted, it is always wrong to lie, always wrong to cheat, always wrong to kill—regardless of circumstances or consequences.

That may work in a simple world. It may have worked centuries ago. It certainly cannot work today, when people are in fundamental disagreement on the moral imperatives themselves. Even the Bible and the Koran have their internal inconsistencies and urge horrifying punishments for what most of us in the twenty-first century regard as fine, upstanding behavior.

Kant had a straightforward rule for deciding whether a particular course of action was right or wrong: universality. In other words, you just imagine everyone doing the thing you are contemplating. Would the world be better off or worse off? It strikes me as simplistic, as too cute by half.

The third school of thought, centering on consequences, emphasizes the outward manifestations of our ethical choices. The best-known example dates back to Jeremy Bentham and John Stuart Mill. Known as utilitarianism, it urges the course of action that creates the most happiness (known as hedonism, the term preferred by Bentham) or benefit (known as utility, the term preferred by Mill) for the greatest number of people. Alone among the three schools of thought, it is so flexible that it opens the moral door to war, enslavement, manipulation, lying and cheating, and economic exploitation.

The doctrine has other severe limitations. Bentham and Mill suggested you could measure hedonism or utility by summing all the “units” of pleasure and subtracting all the units of pain. For a whole society, find a mean and multiply by the population. Think of this as the utilitarian calculus.

The problem becomes evident in a classic illustration. It involves a healthy man and four mortally ill persons waiting for organ transplants. The four can survive by killing the healthy man and harvesting his heart, lungs, kidneys and liver for their own use. One person would die in the process. Four persons would live because of it. That alone would satisfy Bentham and Mill’s utilitarian calculus. But who among us would actually do it?

You cannot do justice to these concepts in just a couple of paragraphs, but it is useful and helpful to be aware of them and to think about them as you wrestle with ethical conundrums.

To the questions that got us started, my answer is: It depends.

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