The article studies dialectics as a way of investigating plurinationality and its counterpart, the ancient Ecuadorian mono-ethnic nation-state. It inquires: 1) what is the ontological foundation of plurinationality? and 2) why does plurinationality as a socio-political approach deny the homogeneity of the liberal State and its correlate external-internal colonialism? It is proposed that the ontological foundation of plurinationality is found in the communitarian society (or social being) and that in its socio-political praxis it denies the fetishization of the liberal nation-state, determined as an instrument of the external-internal colonialism of society. The research conceives and applies the dialectical analysis of concrete reality and the law of universal contradiction as inherent in the social being and the thought that reflects that reality. The study concludes that: 1) the dialectic comprises the category of totality and is useful for the analysis and explanation of society as a whole, of the parts to the whole and of the whole to the parts, in mutual universal interrelation; 2) the community society is an ontological objectification of plurinationality and is manifested in the ethnic-cultural diversity of Ecuador, with distinct historical temporalities, and in opposition to the colonial and republican economic-social formation; and 3) the fetishization of the liberal nation-state as an instrument of the external and internal colonialism of Ecuadorian society is still in force and continues to fulfil the same function through the processing of the coloniality of power, the ontological invisibilization of the other (alter) and racist colonial differentiation.