The role of the EU in that peace has been questioned in this referendum campaign by those who believe that this particular pedestal belongs rather to NATO. So it is important to consider the difference between the EU and NATO, their roles and the difference between building a peace and mounting a defence.
Here is our four things you should know about Britain's influence, peace and security beyond its borders, whether in or out of the European Union.
I: NATO is a military alliance, assembled for security not peace
NATO has roots in the Allies of the two world wars. But it was founded as the military alliance of the West - a treaty bound agreement for collective defence against an aggressor - that was sought out as a counter-balancing power to Stalin's Soviet Union, which was casting a large shadow over Western Europe at the end of the 1940s.
NATO, from its inception under American leadership, has undoubtedly been at the forefront of many of Europe's major conflicts and disputes. In the South and East of Europe, beyond its borders, NATO where heavily involved in the former Yugoslavia, intervening and providing peacekeepers after and today in Syria.
Despite far reaching influence, NATO remains a military alliance. By contrast, as the Cold War went on a third group emerged between the Communist East and the Capitalist West, whose structure was instead an economic alliance.
II: The EU began by using economics to bring lasting peace to Europe
The European Union is the result of civil, rather than military, efforts to bring the people of Europe together. From the start, its methods have been classically liberal - a pillar of free trade economics to prevent war, by materially binding countries by mutual dependence, and a pillar of human rights, that guarantees respect for all of Europe's immensely diverse people, whether as groups or as individuals.
In its time the EU has seen the reconciliation of France and Germany, making war between them unthinkable, and the introduction of democracy to Greece, Spain and Portugal - expanding the EU, and European values and standards as they have become members.
The successes of Europe speak to a different approach to security. By building a peace than brings together a group of people, resolved on a set of principles that stretches beyond nations and borders - beyond tribes and their territories - and encouraging people to recognise their commonality, accept their differences, and choose cooperation, there can be the security that rises from peace and friendship.
III: Europe is threatened by a battle of values, not by force of arms
A military alliance can only offer so much influence on these matters. It cannot address matters of domestic politics without wading in very dark waters. Those who would choose the military alliance over the economic would be literally choosing security over peace, rather than trying to develop both.
A military alliance such as NATO may offer some surety against, for example, the rising militarist authoritarianism of Vladimir Putin's Russia. But what about those countries, in Europe, admiring of his example, who have begun to emulate him at home and come under Putin's sway internationally?
From France, with its Front National, Hungary, with Jobbik, and Poland, with the Law and Justice Party, these countries are members of both the European Union and NATO. Would these parties face expulsion from NATO if they embrace the very authoritarianism that it was set up to oppose? What can NATO do, with all its military power, to influence this struggle for the soul of Europe?
Like the threat of Islamic extremism, this isn't a battle being fought by great powers - gigantic monoliths possessing overwhelming kill power. Influence in such a contest is won, not by arms on a battlefield, but through thousands of civic debates, through effective public services, through the positive opportunity for integration and in millions of small acts of tolerance, decency and welcome.
With integration over nationalism, open borders over closed, in dozens of policy areas, the EU has tried to promote a set of values that stands markedly apart from those of Putin's national authoritarianism or the fanatic totalitarian religious extremism for Islamic fundamentalism.
IV: In the EU, influence is not restricted to states
The European Union exists to bring Europe peacefully together and comes packaged with a commitment therein to human rights, and to democracy. Europe's incomplete integration ensures that how the politics of these values plays out is advertised usually in the crude terms of British, or French, or German interests, or those of two dozen other nation-state members.
Yet, as the movements offering the greatest source of hope for progressives right now show, influence can be exercised in Europe beyond that controlled by the state governments themselves.
The citizens movements of Spain, governing cities and provinces on the principles of municipalism, pushing the municipal cause have a taken a larger view, one more outward looking than might be expected from local politics. They look to help their communities by building alliances between municipalities, between cities, across the entire continent, to bring democracy closer to the people and to bring those citizens together in solidarity.
To that end, the municipal movement governments of cities in Spain have begun meeting directly with the administrations of other cities in Europe. Therein can be found the beginnings of the next great progressive movement - and it has been made possible in the present by the work of decades within the EU.
What do progressives want to influence?
For progressives, the future, the path to their aims - for justice, liberty, equality, progress - still runs the international road. In Europe, that still means looking outward, looking at politics on a continental scale. To that end, the European Union remains the infrastructure that we have.
The EU certainly isn't perfect, but exiting one continental system without another supporting progressive values to join, when so much for the Left depends on international cooperation, is reckless and wasteful. Between voting to remain and voting to exit, voting to remain is the only option that chimes the broad vision.
But for progressives, matters don't rest there. The EU is incomplete. It is under the control of a austere conservative political consensus and under threat from a set of nationalist authoritarian parties who want to regress politics by a century.
Pulling away will do nothing for the peace and security of those who cherish values like openness and tolerance, who believe in standing for solidarity, standing for common values and standing for the common good, need to stay and engage even as other hearts turn colder.
This is Part 3 of a multi-part series, "The Alternative Guide to the EU Referendum" - click here to go to the introductory hub
