On Monday, Immigration Minister Jason Kenney directed that anyone taking the citizenship oath must bare his or her face. Muslim women who wear a veil and refuse to comply will not be permitted to take the oath. And if they don't take the oath, they can't become citizens.

I'm not going to debate the wisdom of that decision. Reasonable arguments can be made for and against it, as one can make reasonable arguments for and against requiring people to bare their faces when they vote or testify in court. The same is true of banning veils in public, as France has done.

But some liberal opponents of these measures go too far when they suggest that veils are no different than turbans, hijabs, yarmulkes or Senators jerseys.

Veils smother identity. They impede communication. They cripple integration. Veils are unlike any other garment in our multicultural wardrobe: They are not only anti-woman, they are anti-social. Even anti-human.

That's because veils cover the face. Not the head, hands, or any other body part. The face. And the importance of the face in human psychology cannot be overstated.

The moment a baby can use its eyes, it starts scanning faces and identifying individuals. Even newborns can distinguish between their mother's face and others'.

As we mature, spotting and identifying faces becomes something we do effortlessly. And automatically. As we go for a walk, we can no more stop ourselves from glancing at the faces of others, and identifying individuals, than we can stop breathing. We all do it. (Or almost all of us. A tiny handful of people with the condition known as "prosopagnosia" lack the ability to identify people by their faces. They suffer terribly as a result.)

It's often said the human brain is a pattern-seeking machine. The pattern it most wants to find is the human face. This is why the most common "false positive" - seeing a pattern where there isn't one - is a face. We see them in clouds. On the surface of the moon. In burnt toast. And what is the famous "have a nice day!" smiley face? Two dots and a curved line. But we don't see two dots and a curved line. We see a person. A happy person.

That's another thing about faces. We don't just use them to identify people. We rely on them to understand what people are thinking and feeling.

Charles Darwin argued in an 1872 book, The Expression of Emotions in Man and Animals, that our common biological origins had produced common forms of emotional expression not only among all humans, but across species. Darwin illustrated his point by juxtaposing the faces of chimpanzees at play with humans laughing.

In the 1960s, researchers sought to put Darwin's hypothesis to the test. If emotional expression is biologically hardwired, they reasoned, it must be universal. A smile can't signal happiness only in Western cultures. It must signal happiness everywhere. Widened eyes and open mouth must mean surprise everywhere. Narrowed eyes and pursed lips must always mean anger. And so on.

Psychologists Paul Ekman and Wallace Friesen took 3,000 photographs of actors expressing one of six emotions - happiness, surprise, anger, sadness, disgust, and fear - and asked test subjects in five culturally distinct countries to identify the emotion portrayed. In every country, people got it right 80 to 90 per cent of the time.

Skeptics noted that the people in all those countries had been exposed to Western media. Perhaps they had learned to read Western forms of facial expression, they said.

Ekman and Friesen responded with an incredible study: In Papua New Guinea, they found a Stone Age tribe that had experienced almost no contact with the outside world, so Ekman lived among them for six months, studying their communications and conducting a series of ingenious experiments. In one, tribesmen were told a story in which, for example, the character was sad. They were then asked to identify the photograph which corresponded to the emotion. Their responses were essentially identical to those of people around the world.

Ekman also asked the tribesmen to imagine they were characters in a story and to make the facial expressions the characters would make when they were sad, angry, and so on. He took their pictures and American university students were later asked to identify the emotions being expressed. Once again, the match was close to perfect.

This work, along with a mountain of other research, has established that the face is hardwired into human psychology. It is the locus of identity. It is the canvas of emotion. We are so supremely sensitive to faces that the tiniest changes in facial musculature - even inadvertent or unconscious changes - can completely alter the apparent meaning of spoken words. Suppressed anger can be revealed, desires surfaced, lies exposed. A subtle affection may be expressed. A deeper trust established.

But none of that can happen if a veil is in the way.

A woman who consistently wears a veil in public is cut off from the people around her. She has no identity. Her ability to communicate and emotionally connect with others is severely restricted. Instinctively, people feel distant from her, and won't trust her, not because they are bigots but because their automatic face-seeking and face-reading is stymied. How can they fully connect with a person who is present but they cannot see?

That is the purpose of veils, after all. They are barriers. They are intended to separate the person behind from those in front. Whether a woman wears a veil voluntarily or not, the effect is the same.

Veils segregate. They are sartorial apartheid.

I can understand why feminists and liberals are reluctant to put it so bluntly. Many of those who loudly condemn veils out of a professed concern for women are simply anti-Muslim bigots. And if women are truly free, shouldn't they be free to wear a veil if they wish?

I share these views. We must protect a stigmatized minority from bigots. We must defend the freedom to dress as we wish to the greatest extent practicable.

But we must also see veils for what they are.