Jean-Paul Sartre's existential mindset was shaped by key influences throughout his life. His experiences during World War II, including imprisonment, reinforced his belief in individual freedom and the absurdity of existence. Sartre's philosophical inquiries stemmed from grappling with the responsibilities of existence and the necessity for individuals to create meaning in their lives. His writings, particularly "Being and Nothingness," explore concepts of bad faith and authenticity, emphasizing the importance of personal choice and accountability. Sartre's reflections on human existence fundamentally shifted modern philosophy, promoting a focus on personal agency in a seemingly indifferent world.