What ideology was not prominent during the 19th century in Europe?

Feudalism is identified as the ideology that was not prominent during the 19th century in Europe because it was largely a system that characterized the Middle Ages. By the 19th century, Europe was undergoing significant political, social, and economic transformations, such as the Industrial Revolution and emerging modern nation-states. During this time, new ideologies gained prominence, including liberalism, which emphasized individual rights and constitutional government; nationalism, which fostered the idea of a unified nation based on shared culture and identity; and Social Darwinism, which applied evolutionary concepts to social and economic issues, often to justify imperialism and class hierarchies. In contrast, feudalism had already declined as power shifted towards centralized states and capitalist economies, making it an outdated social structure during the 19th century.