WHAT WE CAN'T NOT KNOW: A GUIDE by J. Budziszewski Spence, 2003 266 pages, $27.95 To order: (888) 773-6782 http://www.spencepublishing.com

In his Autobiography, G. K. Chesterton relates how he rediscovered faith while immersed in the effete, decadent world of art for art's sake: “It was not that I began by believing in supernormal things. It was that the unbelievers began by disbelieving even in normal things.

It was the secularists who drove me to theological ethics, by themselves destroying any sane or rational possibility of secular ethics.”

The perverse precepts of a minuscule segment of Western society at the turn of the 20th century have been mass-produced, with typical American efficiency, on college campuses for almost two generations. Lawlessness — or, more accurately, the law of the jungle — has become the new “orthodoxy.”

In this book J. Budziszewski, professor of government and philosophy at the University of Texas, sets out to defend commonsense morality against the determined forces of relativism, skepticism and politically correct “tolerance.” I am happy to report that he engages his foes in full gear and fine fettle.

“People become angry when one asserts the moral law,” he writes. “This outrage is itself an amazing fact. It needs to be explained.”

Budziszewski covers much of the same material that might be presented in a first-year college course on Catholic moral theology: the natural law, the nature and workings of conscience, the first principles of morality (for instance, the Golden Rule) and how particular moral imperatives like the Ten Commandments follow therefrom.

He cites St. Thomas Aquinas effectively, yet his message for the most part is not specifically Christian. Rather, the author tries to formulate arguments that will provide a common ground for all people of good will who realize that being human necessarily has moral consequences.

“The desire to know truth is ardent, but it is not the only desire at work in us,” he writes. “The desire not to know competes with it desperately, for knowledge is a fearsome thing. So it is that often-times we groan about how difficult it is to know what is right even though we know the right perfectly well.” Underlying such frank discussion is a vivid sense that an identifiable, standard-issue human nature exists, but that something has gone wrong.

Indeed, we are programmed, in a sense, to distinguish right from wrong; this is part of “what we can't not know.” “The mind is so designed as to acquire [first principles] on its own, as the eye is designed to see on its own,” he points out. “What we call teaching only helps the process along.”

Budziszewski gives a remarkably thorough presentation of natural-law thinking by resting his case upon four pillars, rather than the usual one or two. These “witnesses” to the basic moral law are: one, deep conscience, that built-in program; two, the intelligible design of the universe; three, the design of our own species (we are not only rational animals but also social beings); and four, the natural consequences of our actions.

At key points the author himself becomes the fifth “witness”: As a former atheist who converted to Christianity and traditional values, he is well acquainted with the intricacies of the battles — both political and interior — that are being fought.

As the title suggests, What We Can't Not Knowis often colloquial in tone. That may be its greatest weakness as well as its greatest strength, for these are serious issues. Yet anyone brave enough to watch a contemporary courtroom drama on TV could enjoy the clash of worldviews here. And this very sophisticated book has rock-solid philosophical and theological foundations.

Americans have expended enormous efforts in unlearning the obvious. Professor Budziszewski, with wit and wisdom, guides readers in relearning what we have known all along.

Michael J. Miller writes from Glenside, Pennsylvania.