The book "Theory of the Lifeworld" by Hans Blumenberg offers an in-depth exploration of the philosophical question of the lifeworld. In this posthumous text, published on the occasion of his 90th birthday, Blumenberg goes beyond the conventional understanding and defines the lifeworld as a hypothetical reality in which there are no unanswered questions or unfulfilled needs. This world of self-evidence presents challenges to philosophy, as it exists in a state where philosophical questions no longer seem necessary. Blumenberg draws comparisons from Kant's concept of the 'thing-in-itself' to the black holes of astronomy to illuminate the difficulties associated with the understanding of the lifeworld. He argues that the relationship between theory and lifeworld must be sought in the experience of loss, with science understood as an attempt to cope with the consequences of the disappearance of self-evidence.