This book presents a unique collection of papers on various philosophical aspects of the unknown and unvoiced truth and reality of the cosmic world. It offers a systematic analysis of the three philosophical theories of Quietism, Agnosticism and Mysticism and introduces readers to the fundamentals of mystical knowledge claimed by philosophical schools of the east and the west. It discusses, debates and deliberates on philosophical issues concerning the acquisition of truth, its objectivity and its various dimensions along with the application of thoughts pertaining to Quietism, Agnosticism, and metaphysical-mystic traditions in philosophy. It examines and precisely defines the scope and limits of knowledge, the respective way of life, its expressions and morality, mystical revelation, ineffability of the ultimate, value realism, and faith and reason - with a primary focus on the classical Indian schools of Hinduism, Buddhism, Jainism, Agnosticism, the Bāuls, Greek traditions, modern western meta-philosophy, and contemporary quietist debate in religion and theology. This insightful collection should be of great interest to independent researchers, students and teachers of philosophy, theology, Mysticism and Agnosticism, cultural studies and religious studies.