As early as the 1920s, federalists like Coudenhove-Kalergi perceived that European nations, which had just devastated one another in a nonsensical fratricide war, were a natural entity that could become a significant global force, if only they could succeed in having a federal constitution. After the second catastrophic war for supremacy of one European nation over the others, Altiero Spinelli expressed the view that the national states had lost their raison d'être, since they could no longer guarantee the political and economic safety of their citizens and should give way to a federation, called by him "the European Union". Federalists, thus, put the cart (the ultimate state of European integration) before the horse (the creation of solidarity among former bitter enemies). They had a bright vision, but had not found the means to reach it.
Functionalists like Mitrany rightly pointed out that international organisations are not an end in themselves, but rather the means of addressing the priorities dictated by human needs and have, therefore, to be flexible and modify their tasks (functions) according to the needs of the moment. In their over-optimism, however, for the creation of a cobweb of really international (worldwide), task-oriented organisations, they overlooked and even mistrusted the peacekeeping and welfare functions of a regional organisation like the European Economic Community.
Closer to the European reality, the transactionalist theory of Karl Deutsch defines international integration as the attainment, within a territory, of a "sense of community" and of institutions and practices strong enough to assure dependable expectations of "peaceful change" among its population. The assertion that the sense of community among states would depend on establishment of a network of mutual transactions is borne out by the experience of the European Communities. However, this experience proves that first comes the formal institutional framework and on it are built the informal transactions and hence the community spirit, necessary for an effective multinational integration.
Relatively close to the Jean Monnet method of "common action which is the core of the European Community", is the neofunctionalist theory , developed mainly by Ernst Haas. Both Monnet and neofunctionalist theorists rejected federalist idealism and brought down Mitrany's functionalism from its international high spheres to the concrete level of several neighbouring states. The Monnet inspired famous declaration of Robert Schuman of 9 May 1950 was quite explicit on the road to be followed by European integration: "Europe ... will be built through concrete achievements which first create a de facto solidarity". Integration was viewed as a process where the constructive functions of the main actors, the common institutions, would induce positive reactions of the political and economic elites, influence the behaviour of other societal groups and bring together the citizens of the different nations. Neofunctionalist logic was built on the "spillover" effect. This meant that economic integration would gradually build solidarity among the participating nations and would in turn create the need for further supranational institutionalisation. Leon Lindberg (1963) defined the "spillover effect" as: "a situation in which a given action, related to a specific goal, creates a situation in which the original goal can be assured only by taking further actions, which in turn create a further condition and a need for more action and so forth".
Many other neofunctionalist assumptions have been proved correct by European experience, notably that: action by interest groups would not be motivated by idealistic pursuit of the common good, but would be self-regarding and goal driven; perceptions by these groups of shifts in the loci of authority and power would increasingly direct their activity towards the developing supranational arena; the supranational scheme of government at the regional level would be the appropriate regional counterpart to the national state, which would no longer feel capable of achieving welfare aims within its own narrow borders. In economic terms, the creation of a customs union would generate pressures for the establishment of a common market and monetary union. The close economic integration brought about would require supranational regulatory capacity. Thus, political integration would follow economic integration.
Some neofunctionalist assertions, namely the withering away of the power-based states system, prompted a strong intergovernmentalist alternative to neofunctionalism, despite the strong European evidence in favour of the latter. The Treaties of Maastricht and Amsterdam have, indeed, disproved Stanley Hoffmann's prediction that states would not compromise their sovereignty by moving their integration from the areas of "low politics" (read economics) to the sphere of "high politics", i.e. foreign and security policy. Liberal intergovernmentalist analysis provided by Andrew Moravcsik (1993) has failed to explain how national interests, voiced by national governments in international negotiations, can merge and allow European integration to prosper.
Although the neofunctionalist theory has come closer to the European integration process, particularly thanks to its emphasis on the spillover effect, some critics rightly point out certain deficiencies in neofunctionalist reasoning. By highlighting the multi-level governance (European, national, regional, etc) of the EC/EU and the interaction of political actors across those levels, Gary Marks et al. (1996) have shown the theoretical trap of imagining either the withering away of the state or its stubborn resilience. Neoinstitutionalists, like March and Olsen (1984), have demonstrated the importance of institutions (not just formally established supranational organs, but also informal interactions) in providing contexts where actors can conduct a great number of positive sum bargains. In our point of view, the neofunctionalist theory should be completed with these missing elements and with another most important factor of the multinational integration process: the gradual formulation, development and multiplication of common policies by the actors of the process. In the next section an empirical approach is advanced taking into consideration this important element.
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 SPINELLI Altiero, "The Growth of the European Movement since the Second World War", in M. Hodges (ed.), European Integration, Penguin, Harmondsworth, 1972.
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 MONNET Jean. "A Ferment of Change", Journal of Common Market Studies, n. 1, 1962, p. 203-211.
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 MARCH J.G. and OLSEN J.P., "The New Institutionalism: Organizational Factors in Political Life", American Political Science Review, No 78.