Next week, Scottish voters will decide whether to declare independence from the United Kingdom. Scottish secession once seemed like a bizarre lost cause, but polls have tightened, setting off alarms in England and throughout the world. Critics outside Scotland think that Scottish independence is a crazy idea for the Scots and a bad example for the world, encouraging other separatist movements in less peaceful regions, with turmoil and financial ruin the sure result. But the commentators are wrong. Scotland should go free if that’s what the Scots want.

The brief against independence is, at first sight, strong. The Scots already enjoy a great deal of autonomy within the United Kingdom. Although the U.K. parliament is the supreme source of law throughout Great Britain, the Scottish legislature makes many of the laws that govern Scotland, and Scottish courts enforce them. Unlike many secessionists, Scottish nationalists can’t complain that they’re being forced to learn someone else’s language or that they have no control over how their children are educated. Scotland receives more money from the U.K. than its citizens pay out in taxes. And a Scottish divorce would be a messy, lengthy process that would distract political leaders for years.

Moreover, independence for Scotland will leave lots of victims in its wake. The many Scots who oppose independence will be forced to live in an independent Scottish state they reject, or move to England. They won’t be able to start their own state and secede from Scotland. The English population will also lose the benefits of living in a larger country. Larger countries tend to be richer and safer. Smaller countries get pushed around. Although the Scottish population is a small fraction of the current U.K. population, the Scottish economy is not negligible, and Scottish territory represents a large fraction of the U.K..

We in the U.S. could also be hurt by Scottish secession. The United Kingdom has been a loyal and powerful ally of the United States in many international conflicts—against Communists, Islamic terrorists, and other foreign ogres. A disunited kingdom, embroiled for years in negotiations over the division of the country, would be a weak and distracted ally.

In the face of such arguments, some commentators blame the secessionist impulse on childish resentment at England, which is widely if falsely perceived as a bully, and emotional appeals to nationalist sentiment by scheming politicians.

But while it’s true that Scottish nationalists often make mystical arguments (as nationalists always do), the case for independence is based on serious policy considerations. Some Scots believe that independence would give Scotland sole ownership of valuable oil deposits off its coast in the North Sea. Although those resources may well be almost depleted, it is possible that advances in oil-extraction technology would enable Scotland to create an oil-financed welfare state like Norway’s.

More importantly, if Scotland were independent, Scots would control the whole array of policy instruments that Scotland now shares with the rest of the U.K.—above all, taxing and spending. The Scots would be able to govern themselves however they want—and that includes putting into place the more generous welfare state that the more right-leaning English public has denied them.

Against the real benefit of greater autonomy, the costs of leaving the U.K. seem abstract. In general, bigger countries are safer than small countries, but there is no serious threat to states of comparable size, or smaller, to a new Scottish state—including Switzerland, Norway, Denmark, and tiny Iceland. Unlike Ukraine and Georgia, Scotland has nothing to fear from its neighbors. And because Scotland will continue to enjoy free trade with Britain, Europe, and the rest of the world, it—like Switzerland, Norway, Denmark, and Iceland—will continue to prosper.

Both nationalists and their critics have obscured the stakes by presenting the question of Scottish independence as either/or when in fact it is a matter of degree. As noted, Scotland already enjoys a fair amount of autonomy within the United Kingdom. Recently, the British government offered Scotland more autonomy—more control over taxes and spending—if it remains in the United Kingdom. If Scotland declines this offer, it will almost certainly be allowed to join the European Union, and so remain a peer of the U.K. in that larger supra-national entity.  Scotland will probably be able to remain in a currency union with the U.K. despite English threats to expel it; if not, Scotland could join the euro or, as Paul Krugman advises, go it alone.

No one plans to build a fence around Scotland. Trade and investment will continue as before. Very likely free movement across the border between England and Scotland will continue as it does among most of the sovereign states of Western Europe. There is a sense—an irony not lost among the anti-secessionists in light of the nationalist rhetoric—that Scotland is not so much declaring independence as abandoning its status as vassal to the U.K. so that it can become a vassal to the EU.

This might really seem crazy. Why exchange one overlord for another? The population of the EU is 13 times that of England and Wales, and so the influence of the Scots on EU policy will be commensurately smaller. But the move actually makes sense. In lying to the left of England, Scottish political sentiment is closer to the continent’s. European policies will be closer to Scots’ preferences than the English policies that they currently reject. Scotland and France have enjoyed a centuries-long dalliance that England repeatedly thwarted; perhaps the advance of communication and transportation technology finally will allow the two countries to consummate their relationship.

If independence is in the self-interest of the Scots, critics can argue that independence is selfish rather than crazy. Many people worry that Scottish independence would inspire other secessionist movements to redouble their efforts, and in other parts of the world national divorces are less pretty than what we are seeing in the U.K. Secessionist groups have a nasty habit of complaining that they are deprived of self-determination and then, once they have their own state, expelling or repressing their own ethnic minorities. The logic of secession seems to portend an unraveling of the state system until the world consists of a billion sovereign households that are constantly at war with each other.

But it is most unlikely that Scottish independence will plant an idea into the heads of nationalists that is not already there. Scotland’s secessionist movement fits into a larger trend of state fragmentation that goes back more than a half century. Since World War II, the number of states worldwide has increased from about 70 to almost 200. Much of this was due to the collapse of empires, but in the last 20 years numerous states have hatched simply because people no longer wanted to live with each other. Five countries rose from the ashes of Yugoslavia in the early 1990s, and 15 from the Soviet Union; since then, additions include Eritrea, East Timor, Kosovo, and South Sudan. The Czech Republic and Slovakia split, as did Serbia and Montenegro. Secessionist movements have also made headway in Spain, Italy, and Belgium, and can be found in numerous other countries throughout the world.

The explanation for this trend is that the benefits of a large country—mainly, security and a large internal market—are of diminishing significance in a world of free trade and relative peace. Under these conditions, nationalist movements based on ethnic and linguistic difference, and cultural values, are likely to flourish. Countries split apart but they remain relatively secure (unless your name is Ukraine or Georgia), and able to trade with each other and others.

The size of a state reflects an equilibrium between constantly shifting centrifugal and centripetal forces. People at once want the economic and security advantages of being part of a large country, and chafe at the loss of political control. How these forces play out in particular regions is too complex for outsiders to understand. Where national aspirations are heartfelt, you’re not going to get far telling them that they can’t start a new state because of the theoretical possibility that bad actors elsewhere in the world will imitate them. Let the Scots have their Scotland.