Philosophical approaches to esotericism are brought together in an examination of how hidden knowledge, mystical traditions, and alternative systems of thought have been understood from the nineteenth century to the present. The book considers questions surrounding rationality, knowledge, spirituality, modernity, and the boundaries between accepted and rejected forms of intellectual inquiry. Rather than assuming a single definition of esotericism, it presents different philosophical perspectives and encourages readers to examine the category itself. Suitable for students and intellectually curious readers, the volume provides a conceptual framework for understanding why esoteric ideas continue to attract attention in philosophy, religious studies, and cultural history.