The term Megali Idea, Great Idea, first appeared on 14th January 1844, in a speech Ioannis Kolettis gave in the course of the dispute between the autochthons and heterochthons. From that point on and throughout the rest of the 19th century it would constitute the driving ideological principle of the young state. Moreover, it functioned as a point of convergence and unification for a fractured society, a society subjected to traditional regional and social oppositions, placing awareness of national identity on a new footing. The thrust of the Great Idea, which could be expressed in the phrase 'national completion', was never determined in any strict and definitive way. Furthermore, it was organized on two stable axes:
a) A general political command which aimed at the political and geographical unification of the Greek populations so that they could be included within the national state. The Byzantine Empire from the years of the Macedonian dynasty constituted the territorial model of expansion of the Greek state, while irredentism - that is, the ideology of liberating the unredeemed people of the same nationality - was legitimized in the field of international relations for the application of the expansionist policy. Finally, the 'civilization of the East' which would be achieved through Hellenization suggested the 'historic mission' of the Greek nation and indicated the direct descent of the newly-established kingdom from Greek Antiquity.
b) There was a general and urgent demand for national unity which seemed to be an indispensable condition for the realization of the political command. The unity of Hellenism in space presupposed its unity in time, its uninterrupted continuity down the centuries. It is in this respect that the historian K. Paparrigopoulos in his work Istoria tou Ellinikou Ethnous restored Byzantism as a link between Greek Antiquity and modern Hellenism at a time when the racial kinship/continuity of ancient Greeks with modern Greeks was questioned.
The certainty of the realization of the political command of the Great Idea which possessed Greek society throughout the 19th century did not accord with the restricted economic and military possibilities of the state, nor with the excessive intervention of the Great Powers. The so-called Ipirothessalika at the beginning of the Crimean War (1854) were the first of a series of unsuccessful attempts to realize irredentism in this century.
However, this did not contradict the principle of the Great Idea. On the contrary, it continued to function as the chief factor for integration into the Greek kingdom, strengthened by the gradual emergence of the antagonistic nationalisms of the other Balkan peoples in the second half of the 19th century.