Sliding Doors

Japanese doors are quite unique.
The 'sliding door' has existed since as far back as the Heian period.
It is a style rarely seen elsewhere in the world, where 'swing doors' are the standard.
In the first place, if you consider space, sliding doors are better.
This is because swing doors require space to open and close, creating dead space that must be accounted for.

So why didn't they become popular elsewhere?
This comes down to technology.
In a word, it's because you have to create 'parallel' surfaces.
With a swing door, even if the shape is irregular, it's fine as long as the door covers the opening.
The shape doesn't even have to be rectangular.
Sliding doors are different.
They must slide, so not only must the floor be flat, but the ceiling and the door itself must be parallel to the floor so that it can slide without getting stuck.
In other words, it requires advanced architectural technology.

I feel that in Japan, where sliding doors developed in this way, the concept of 'boundaries as an idea' has become very strong.
With a swing door, you can just lock it.
You could even attach a bolt.
A swing door also functions as a device that physically prevents entry.
But what about a sliding door?
Well, you could lean a broom against it from the inside to keep it from opening.
That's an exception, though; basically, they aren't locked.
The culture of locking doors itself was introduced from the West after the Meiji era.
Even if it is a private room, it isn't locked, and it doesn't function as a physical barrier.

Even today, in traditional Japanese inns, the room entrances are designed so they cannot be locked.
Yet, people do not enter the rooms.
This is because they hold the conceptual belief that they must not enter.
I believe that this conceptual boundary is particularly strong in Japan.

For example, an audience with the highest authority.
In depictions of an audience with a king, there are usually two guards standing in front of a large swing door.
At a command, the large doors are opened, and the king sits at the end of a path created by the guards.
Physically opening the door is difficult, and in the first place, you would be blocked by the guards.
On the other hand, an audience with the Emperor.
Often, the fusuma (sliding screens) are opened, and the Emperor is on the other side of a bamboo blind.
There is almost no physical barrier; you could reach the Emperor or see him if you really wanted to.
However, there is a psychological barrier—the conceptual idea that one must not look directly at the Emperor or behave disrespectfully.

These kinds of conceptual boundaries—where it isn't physically impossible to go, but you feel like you shouldn't—exist in many places.
You could enter the main hall of a temple or shrine if you really wanted to.
You could also enter the back area of a convenience store, even though there is a sign saying 'Staff Only.' (Though some places do have locks.)
In contrast, in the West—at least in the UK where I have lived—the back areas were locked.

Even without physical devices, the conceptual boundary of 'I feel like I shouldn't do this' is particularly strong in Japan.
Perhaps self-restraint has been cultivated even without explicit prohibitions.
I think it is precisely because Japan has developed such strong conceptual boundaries that people have developed a keen sense for what should not be done, which has led to a high level of morality.