Both the American Declaration of Independence and the French Declaration of the Rights of Man are foundational texts of classical liberalism. They emphasize individual rights, equality, and the limitation of government power, reflecting the Enlightenment ideals that defined the liberal political tradition in the late 18th century.

Cultural nationalism defines the nation as a community bound by shared cultural heritage, language, and traditions rather than purely political or civic institutions. It emphasizes the preservation of a distinct identity and the belief that the state should reflect the unique cultural character of its people. While it often manifests as a desire for a separate identity, it is distinct from revolutionary nationalism, which focuses on radical political change.

Carlton J. H. Hayes was a distinguished American historian and diplomat whose work focused extensively on the development of nationalism in Europe. His book 'Essays on Nationalism' is a classic text that examines the historical, cultural, and political dimensions of nationalist movements. Hayes argued that nationalism functions as a secular religion, shaping modern identity and state loyalty, and his analysis remains a foundational reference for students of political history and the evolution of the nation-state.

In the context of modern political identity, the nation-state remains a primary focus of individual loyalty. This phenomenon is rooted in shared history, cultural heritage, language, and collective experiences, which foster deep-seated bonds that often outweigh abstract notions of global citizenship or universal human allegiance in the minds of the populace.

The principle of national self-determination asserts that nations have the right to choose their own sovereignty and political status. The Congress of Vienna, while primarily focused on restoring order, sparked nationalist sentiments, and President Woodrow Wilson's 14 Points explicitly championed self-determination as a cornerstone of the post-WWI international order, making both significant in the evolution of this concept.

The modern state is fundamentally defined as a 'nation-state'. This concept emerged following the Treaty of Westphalia, where the state became identified with a specific territory and a population sharing a common identity, culture, or history. The nation-state model emphasizes sovereignty, territorial integrity, and the alignment of political boundaries with national identity, which remains the dominant form of political organization today.

National liberty refers to the independence of a nation-state from foreign control, combined with the internal freedom of its people to govern themselves. It is a collective form of liberty that ensures a country can determine its own destiny, maintain its territorial integrity, and manage its internal affairs without external coercion or interference from other powers.

Dual or multiple citizenship is a legal status where an individual is recognized as a citizen of more than one country simultaneously. This occurs due to varying national laws regarding birthright (jus soli) and descent (jus sanguinis). Many modern states allow their citizens to hold additional nationalities, meaning an individual can indeed be a legal member of more than one state at the same time.

Nationality refers to a person's belonging to a specific ethnic or cultural group, often defined by shared history, language, or culture. Unlike a 'nation-state' which implies political sovereignty, nationality is a sociological or cultural status that can exist independently of political independence or statehood, allowing it to survive even under colonial or foreign domination.

The French Revolution of 1789 is considered a pivotal moment in the development of modern nationalism. By promoting the ideals of liberty, equality, and fraternity, it shifted the focus of loyalty from the monarch to the nation-state, thereby inspiring nationalistic movements across the European continent.