Søren Kierkegaard is widely regarded as the father of existentialism. His writings explored themes of anxiety, despair, and the search for meaning in life.

Intentionality is the central concept in phenomenology. It refers to the directedness of consciousness towards objects and the world.

Friedrich Schleiermacher is credited with developing the concept of hermeneutics, which is the study of interpretation and understanding.

Jacques Derrida is considered the founder of post-structuralism, a philosophical movement that critiques the traditional notions of truth, meaning, and representation.

Friedrich Nietzsche's philosophy is centered around the concept of the will to power, which he believed is the fundamental driving force behind all human behavior.

Jean-Paul Sartre's play 'No Exit' is a classic existentialist work that explores themes of freedom, responsibility, and the meaninglessness of existence.

Martin Heidegger's concept of 'being-towards-death' is a central theme in his existentialist philosophy, emphasizing the finitude and mortality of human existence.

Hermeneutics is the study of interpretation and understanding, particularly in relation to texts and cultural artifacts.

Friedrich Nietzsche's concept of the 'Übermensch' or 'superman' represents an ideal human being who has overcome traditional moral values and achieved a state of self-realization.

Albert Camus' philosophy of the absurd centers around the idea that the world is fundamentally meaningless and irrational, and that humans must confront this absurdity with courage and resilience.

Linguistic philosophy is a branch of philosophy that investigates the relationship between language, meaning, and truth, often focusing on the analysis of ordinary language.

Friedrich Nietzsche's concept of the 'eternal return' posits that every moment in time will repeat itself infinitely, challenging individuals to live their lives with purpose and authenticity.

Jean-Paul Sartre's concept of 'bad faith' refers to the state of self-deception and inauthenticity in which individuals deny their true freedom and responsibility.

Metaphysics is the branch of philosophy that explores the fundamental nature of reality, existence, and being.

Martin Heidegger's concept of the 'Dasein' or 'being-in-the-world' emphasizes the interconnectedness of human existence with the world and the significance of everyday experiences.