Many spiritual traditions speak of a 'guardian' or 'dweller' who protects the threshold to the spiritual world, warning the unprepared to pause in their quest for access to higher knowledge. The Guardian reveals the consequences of our negative actions and points to the full reality of our untransformed nature. This experience is said to be one of the deepest and most harrowing on the inner path, but is an essential precondition to any form of true initiation. The words 'Know thyself' were inscribed at the forecourt of the ancient Greek Temple of Apollo. Those who sought initiation in 'the mysteries' were thus instructed first to look within themselves. Likewise today, as spiritual seekers we need true self-knowledge, to distinguish between what belongs to our consciousness and what is objectively part of the spiritual environment. Rudolf Steiner taught that as long as we draw back from such knowledge, our spiritual quest will be unsuccessful. When we begin engaging with anthroposophy, it becomes clear that Steiner's teachings are not a doctrine or set of dogmas, but a path towards deeper insights. In this essential handbook, the editor has drawn together many of Rudolf Steiner's statements on the intricate and arduous path of self-knowledge, offering ongoing support and guidance. Chapters include: The Importance of Self-Knowledge for Acquiring Higher Knowledge; Seeking to Form an Idea of the 'Guardian of the Threshold'; The Guardian of the Threshold and Some Characteristics of Supersensible Consciousness; Morality on the Path of Knowledge; Self-Knowledge and Nearness to Christ; The Powers of Christ in Our Own Life; Knowing Ourselves in the Other; Self-Knowledge - World-Knowledge.