In my Roman days, I once passed through Cairo. I stayed at the French Jesuit College there. One day, I visited various mosques, which were quite impressive. To enter any mosque, it was necessary to remove one’s shoes. You placed them by the door. I recall wondering what I would do if they were not there on my return. But this was holy ground.

The requirement of standing before the Lord unshod is often found in the Old Testament. The Masons have an unshodding rite as part of initiation ceremonies. To be shod means to protect one’s feet; whereas inside the temple, one does not need protection from the Lord.

Another Christmas season, I was in Japan. A Jesuit friend kindly invited me to accompany him. We were invited for tea with a Japanese family, friends of his. Again on entering the home, we removed our shoes. We were given slippers.

My Chinese niece-in-law also follows this custom in her house. Whether it is a question of cleanliness or piety or both in the oriental case, I am not quite sure. But once you get used to it, it is not a bad custom.

After 9/ll, whenever I traveled by air wearing a black suit and Roman collar, I was taken aside by security and examined for hidden weapons. Since the “tennis-shoe bomber,” one Richard Reid, was detected on an American Airlines flight from Paris to Miami in December 2001, all subsequent airline passengers, billions of them, have had to take their shoes off while going through airport security.

I have no idea what the cost of this extra precaution might be worldwide. In more recent years, if one is over seventy-five, he is not required to remove his shoes. Old boys don’t bomb. My experience is that at least half of the time, however, my ordinary shoes turn on some alarm. Now I unshod myself anyhow, without a murmur.

I do not know if Japanese airlines provide slippers on their flights. Richard Reid, the shoe bomber, was an Englishmen who converted to Islam while spending time in jail for theft. Due to his loaded tennis shoes, the whole world has had to follow this Muslim custom of taking shoes off, only now also in airports.

I am not sure if Allah recognizes this unshodding as valid homage. It does show how a pious custom can become a civil law designed to protect everyone. We cannot trust everyone not to fill his tennis shoes with explosives. So far it has worked. Yet, I do not see why someone has not invented a machine that would do the trick while letting us wear our shoes.

In a sense, the whole world is now held hostage both to a religion and security. Had Reid managed to blow himself up with all the (at that time) shod passengers on American Airlines, he might well have been considered a martyr by pious jihadists.

The story continues. Pope Francis on Holy Thursday was internationally noticed when he washed the unshod feet either of a woman or a Muslim, often the same person, who is both. Christ only washed the feet of the disciples. This washing was not so much analogous to Moses, unshod on holy ground. The pope seems to think that the ceremony designates humility or God’s universal jurisdiction.

Washing feet is a cleanliness custom of eras when everyone walked barefoot or with sandals on dusty or muddy roads or fields. It would seem this is also the Chinese custom. Many houses will have rooms where we can change our muddy boots for more comfortable slippers in order not to soil the floors in the living areas.

So what is it that we see when someone has to take off his shoes, to pass unshod into a security cage or a mosque or a home? Many commentators have been concerned that the Holy Father does not realize what the Muslim world sees when it watches him washing the feet of a Muslim. It is, to them, a sign not of humility but of submission.

I cannot go into a mosque and tell the custodian: “Look, I am not a Muslim. We wear shoes inside churches. You are violating my ‘rights’ by making me take my shoes off.” Likewise, if I tell the TSA guard that I have a “right” to wear shoes, he will, like the mosque custodian, politely toss me out.

Christ’s washing of Peter’s feet had to do with the function of authority among the disciples. To be unshod on holy ground meant to recognize God’s sphere. The Latin words fas and nefas mean to be inside or outside of what is holy, inside or outside the temple. The simple act of removing of our shoes can lead us to reflect more carefully on which God we serve.