Søren Kierkegaard, a Danish philosopher, is widely regarded as the father of Existentialism. His works explored the themes of individual existence, freedom, and the meaning of life.

Phenomenology, as developed by Edmund Husserl, focuses on the study of consciousness and the structures of experience. It seeks to understand the world as it is directly experienced by individuals.

Martin Heidegger, a German philosopher, introduced the concept of 'Being-in-the-world', which emphasizes the interconnectedness between human existence and the world.

Jacques Derrida, a French philosopher, is known for his theory of 'deconstruction', which involves critically examining texts and discourses to reveal their underlying assumptions and power structures.

Hermeneutics, a philosophical approach, centers on the interpretation of texts and the understanding of their meaning. It explores how individuals interpret and make sense of written or spoken communication.

Roland Barthes, a French literary theorist, introduced the concept of 'the death of the author', which suggests that the author's intention is not the sole determinant of a text's meaning.

Post-Structuralism, a philosophical movement, challenges the traditional binary oppositions that structure thought and language, such as subject/object, mind/body, and truth/falsehood.

Michel Foucault, a French philosopher, introduced the concept of 'the gaze', which examines how power relations are inscribed in the way we see and are seen.

Judith Butler, an American philosopher, is renowned for her work on gender performativity, which explores how gender is not a fixed identity but rather a set of socially constructed practices.

Critical Theory, a school of thought associated with the Frankfurt School, focuses on the analysis of social and political power structures and their impact on individuals and society.

Michel Foucault, a French philosopher, introduced the concept of 'the panopticon', a model of surveillance and control that operates through the internalization of power.

Jürgen Habermas, a German philosopher, developed the theory of communicative action, which focuses on the analysis of social interactions and the conditions for rational discourse.

Gilles Deleuze and Félix Guattari, French philosophers, introduced the concept of 'nomadism', which explores the idea of movement, becoming, and deterritorialization.

Slavoj Žižek, a Slovenian philosopher, is known for his work on the critique of ideology, particularly in relation to capitalism, politics, and culture.

Gilles Deleuze and Félix Guattari, French philosophers, introduced the concept of 'the rhizome', a non-hierarchical, interconnected network that challenges traditional notions of structure and organization.