Spiritual knowledge is the supreme among all types of knowledge. The Shruti says ” Advaita Darshanam Jnanam”. Vision of non-duality is true knowledge. The Upanishads have revealed this non-dual knowledge which is to be awakened through the process of Shravanam (Listening), Mananam (Reflecting), and Nithidhyasanam (Meditation). This book presents the doctrine of Upanishad (Upanishad Matam) in a very rational and lucid manner in the perspective of modern thought.