Money is the means through which that unity is established. Country join up because it makes economic sense, because that's a short term reward, the long term r

Money is the means through which that unity is established. Country join up because it makes economic sense, because that's a short term reward, the long term reward which is less chance of war, is more uncertain and politicians rarely get the chance to be allowed to think long term about big decisions like this. Hence the whole Brexit fiasco in the first place.