Which political belief systems developed as ideologies during the 19th and 20th centuries?

During the 19th and 20th centuries, several influential political belief systems emerged or evolved as ideologies, largely shaped by the currents of democracy, industrialization, and global conflict.12

19th-Century Ideologies

The 19th century saw the rise of three primary ideological currents that defined reactions to the democratic and industrial revolutions:1

• Liberalism: Generally welcoming of industrial and democratic changes, liberalism emphasized individual freedom, capitalism, and constitutional government. It became a preeminent reform movement, driving efforts to abolish slavery and expand the franchise.13
• Conservatism: Often retrospective, this ideology prioritized tradition, authority, and civility, frequently expressing skepticism toward the rapid shifts brought by democracy and industrialization.1
• Radicalism: While accepting democracy, radicals sought its total extension across society and were typically antagonistic toward capitalism.1

Additionally, nationalism—the belief that loyalty to the nation-state should surpass other interests—became a powerful force during this era.4

20th-Century Developments

The 20th century saw the refinement of earlier ideologies and the emergence of totalitarian systems:52

• Totalitarianism: This phenomenon included Marxism-inspired revolutionary doctrines (such as the Soviet model) and various forms of fascism, which rejected individualistic liberalism in favor of state supremacy.52
• Modern Political Philosophy: Beyond these, the 20th century saw the continued development of liberalism, the rise of postmodern critiques questioning objective political values, and the emergence of feminist philosophies challenging historical gender-based power structures.2