They’re called tzompantli: racks of human skulls, cut from the victims of Aztec human sacrifice.

If you thought any of the 16th-century accounts of Aztec culture were exaggerated, think again.

Recent excavations in Mexico City on a street behind the cathedral have discovered racks of skulls that once filled a space larger than a basketball court.

In an area 36 by 14 metres, the skull racks towered 5 metres high. Two towers with rings of skulls also flanked these skull racks.

Some people consider such archaeological evidence to be a proof of value relativism. Every culture, they say, has different ideas of right and wrong. Who are we to judge?

We are horrified by human sacrifice, they say, but it was once part of the Aztec way of life. No doubt we are doing horrible things today, but who is able to escape from the values our culture conditions us in?

How do we know which values are superior?

And how do we know which values are superior, if our culture conditions us with an inevitable subjective bias?

The Catholic philosopher Dietrich von Hildebrand, famous for his battle against Hitler, has an excellent response to relativism in his book Christian Ethics (1953).

Ethical relativism is a subdivision of any general skepticism about our ability to know what things have intrinsic value (“importance-in-itself”).

But such general skepticism is self-contradictory, because it claims to know the objective truth about the absence of objective truth.

Yet how do we explain the differing views of good and evil among different peoples and cultures? For example, the Aztecs saw human sacrifice as a great good.

Hildebrand argues it is “an invalid syllogism” to infer, from the premise of “the diversity of moral judgments,” the conclusion “that moral values are relative, that there exists no moral good and evil.”

“The truth of a proposition does not depend upon how many people agree to it, but solely upon whether or not it is in conformity with reality,” notes Hildebrand.

If the Aztecs practiced human sacrifice, believing it to be a great good, how is it they came to such an unreal and erroneous view?

Even if different cultures have different views of human sacrifice, Hildebrand points out that “in all these diversities the notion of an objective value, of a moral good and evil, is always presupposed.”

The Aztecs considered human sacrifice to be an objective value.

In other words, the Aztecs considered human sacrifice to be an objective value and a supreme moral good. As the Greek philosopher Aristotle said in his Nicomachean Ethics, no person or culture acts without aiming at a value considered to be good.

Yet, whenever our intellect and will are not rightly disposed, it is difficult to perceive the truth about values. “Reverence, a sincere thirst for truth, intellectual patience,” and spiritual sensitivity are all needed to attain any deeper knowledge, says Hildebrand.

Additionally, to perceive the truth about moral values, we need “a readiness of our will to conform to the call of values, whatever it may be,” otherwise we end up with a bad will that blindly and stubbornly rationalizes our actions, by constructing false values.

The towering skull racks of the Aztecs testify to their value blindness about human sacrifice. Rather than proving moral relativism, the skull racks instead prove just how wrong people can be at perceiving true moral values.

 “Once we have grasped the roots of moral value blindness, it will no longer be astonishing that there exist such diversities of value-judgments; rather we shall be astonished at how many agreements nevertheless exist among all tribes, epochs, and individuals,” writes Hildebrand.

Furthermore, humans are spiritually capable of transcending the moral value blindness of their cultures. It may be difficult to do, but great individuals do bear prophetic witness and summon us to better perception of objective values.

Relativism fails to account for the noble human experience of “great moral personalities,” like Socrates, who pierce the customs of the cultural environment that make people blind to morality, notes Hildebrand.

One of the great objective values a culture can enshrine is religious freedom.

One of the great objective values a culture can enshrine is religious freedom, allowing reverent and intellectually patient people to pursue the truth for which humans thirst. 

Everybody is capable of “discovering parts at least of the true world of values,” says Hildebrand. Allowing people to be free to make such discoveries, which increase value perception, thereby benefits all of society. 

The only other option is to build our own version of skull racks as testimony to the violent power of central planning and social engineering.

Yet the Aztec skull racks should warn people about value blindness. Could what you cling to so zealously in fact be horribly wrong?