To understand the Year of Jubilee, we must momentarily set aside our modern understanding of private property and real estate. The Judaic system was not based on deeds and brokers, but rather on history and family blood. It sacramentalized the simple warmth and deep history of "the old homeplace."
In a sense, the land owned the family more than the family owned the land. That is why, in verse 13, it speaks of everyone "returning to their possession." Land doesn't wander about and get disoriented - people do. Perhaps you have noticed how the forest never gets lost.
So every 50 years, every family in the nation returns to their historic inheritance. The donkeys brayed, the children shouted, and the dust flew. Creaking carts of household goods and herds of startled livestock criss-crossed the countryside. It must have been quite a scene - a sort of mini-exodus, with all the accompanying chaos and drama.
In the interim, property was "bought" and "sold" conventionally, although the price was pro-rated based on the relative distance or immanence of the Jubilee (vs. 15-16), since this event unilaterally nullified all of these transactions.
What is fascinating about this idea is that it is neither truly socialist or truly capitalist, but rather a hybridization of the two. The capitalist has no Year of Jubilee, while the socialist has a perpetual one. Both ideologies contain damaging excesses.
Competition and incentive are necessary for a healthy economy. God provided a generous window for the talented and ambitious to expand their business, expand their assets, and reap (literally) the appropriate rewards from their effort.
This headlong expansion, however, was capped at 50 years, effectively preventing the formation of mega-corporations like we have today - these hallmarks of full-blooded capitalism like Wal-Mart or Microsoft. Families were given the chance to make a new start on a level playing field, which would serve to stimulate an atmosphere of industry and possibility, rather than creating an endless spiral of apathy and despair.
The beauty and ingenuity in this system is that it restores equality without resorting to robbery, which is more than can be said of socialism. There is no arbitrary seizure of goods, (with the consequent throat-slitting of honest labor and enterprise,) because the equalization is anticipated beforehand, and woven into the economic fabric of the society.
I do not know the value or viability of applying this model to modern society, which is no longer predominately agrarian. It is nonetheless a striking economic strategy, and one which may have useful applications that are yet to be discovered.
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