This textbook reviews for the first time the thinking of six major existential philosophers; Søren Kierkegaard, Friedrich Nietzsche, Martin Heidegger, Jean-Paul Sartre, Maurice Merleau-Ponty, and Simone de Beauvoir with respect to their ideas about human development. Martin Adams presents a philosophical and psychological analysis, and critically evaluates the different ways that existential philosophy can illuminate the way we all strive for meaning and purpose in life. Written in a detailed, well-structured manner, this text offers a fundamentally different way to understand not only life in general but the practice of psychotherapy in particular.