Watching the news of the past few weeks, one is struck by how countries that have spent much of the past 50 years espousing the concept of open borders, and even a "borderless" world, are reneging on that policy.
The mass flow of refugees from the war-torn countries of the Middle East and the famine-ravaged countries of Africa has resulted in a reconstruction of physical borders in and around Europe.
Physical barriers between states, we had been led to assume, were no longer necessary in an era of peace and neighbourly relations.
In Israel, where our borders have always been a point of debate, and where only two (those with Egypt and Jordan) have ever received full international recognition by virtue of the peace treaties that have been signed, many borders were left open.
For well over 30 years, the border between Israel and Egypt was not fenced or walled in, while the border running along the west of the country from Elat-Aqaba in the south to the Jordan-Israel-Syria meeting point in the north, was limited to a flimsy, often dilapidated, fence, which few on any side had any desire to cross.
The founding fathers wanted Israel to integrate into its region
In Israel, borders have returned with a vengeance. Starting 10 years ago, we unilaterally constructed the separation / security barrier / fence / wall (delete whichever term you are uncomfortable with), separating Israel from the West Bank and effectively closing the border to Palestinians.
Anyone who has ever used any of the five major crossing points along the route of the separation barrier will know that, while Israel may be averse to calling it a political "boundary", it functions like any international border, with documents examined, trucks inspected for illegal goods, and customs duties levied.
Israel has also constructed a new fence along the entire length of the Israel-Egypt border. Ostensibly to prevent the unhindered flow of migrants from Africa, this too has become a major new security consideration as fundamentalist groups have moved into the Sinai Peninsula.
This border is now equipped with highly sophisticated surveillance technology and is managed carefully, as Israel attempts to prevent radical groups from launching attacks.
Meanwhile, Prime Minister Netanyahu has announced that one of the major infrastructure projects of the next decade will be the creation of a new, fortified border along the entire western length of the country, starting at Eilat in the south and running the entire length of the Arava and Jordan valleys.
This, too, is seen as fulfilling a double role - preventing the flow of migrants from war-torn Syria and Iraq to the east, and enabling greater control over the movement of potential terrorists such as Daesh, some of whose members have already taken control of areas close to Israel's border with Syria in the Golan Heights.
None of these borders can stop the rockets, be they from Gaza, South Lebanon, Sinai or, potentially in the future, Syria. The rockets and missiles currently stocked by Hizbollah and Hamas can reach almost every point in Israel. It is the Iron Dome anti-missile system, rather than the border, that is front line against this threat.
It is somewhat ironic that Israel is now in the process of completing the fencing in of the entire country, a sort of self-ghettoisation from the outside world. This is in direct contrast to the dreams of the founding fathers, who saw Israel as eventually integrating into its region - if not culturally, then at least economically and politically.
No longer would Jews have to sit behind walls to protect them from anti-Jewish hatred of those on the other side. No longer would a Jewish state allow others to enclose them inside walls and prevent them from moving freely into the surrounding environment.
But the economic and political realities of the past decade have proved overwhelming. Borders are collapsing in the rest of the Middle East, states are crumbling and undergoing territorial reconfiguration.
In this context, borders are rapidly regaining their previous significance and importance.
