The democratic constitution should be the embodiment of the sovereignty of the nation. In such a constitution the nation autonomously establishes the tenets and rules of its functioning. The concept of the nation forming the basis of the constitution affects its shape and determines its interpretation. Having analysed the canonical works considering philosophy and theory of democracy (Kant, Rousseau, Kelsen, Schmitt, Rawls, Habermas), one may develop two fundamental (ideal in Weber‘s perception) kinds of the nation: homogenous (emphasizes the basic unity of citizens) and heterogeneous (underlines pluralism and diversity of citizens‘ goals). Adoption of ideal types for the description of current changes in Poland enables the presentation of the gradual modification of the nation concept. It changes the interpretation of the constitution and affects the purview of the law-makers‘ legislative delegation. Eventually, such a modification may lead to an informal change of the constitution.