There are 18 Upanishads, Upanishad means sitting close; this implies the students sitting down near their Guru to learn. In the splendid isolation of their forest abodes, the philosophers who composed the Upanishads contemplated upon the various mysteries of life and its creation – whether common, or metaphysical. The answers were however not open to all, but only for selected students. The reason for this was simple: not everyone can handle knowledge. The composition of the Upanishads marks a significant and stride forward in the direction of knowing the mystery of earth's creation and one comes tantalizingly close to the answers. Through episodes, commentaries, stories, traditions and dialogue, the Upanishads unfold the fascinating tale of creation, life, the essence of life and of that beyond to the seeker of truth. There is no exact date for the composition of the Upanishads. They continued to be composed over a long period, the core being over 7th -5th centuries BC. The Upanishads were originally called Vedanta, which literally means the conclusion to the Vedas. In the Upanishads, views about Brahman (the Absolute, or God) and atman (one's true self) were proposed. The core of the teachings of the Upanishads is summed up in three words: Tat Tvam Asi … you are that.
The Bruhad-Aaranyak Upanishad is widely accepted to be the most important of all Upanishads. It has three khand or parts. The Madhu Khand contemplates on the relationship between the individual and the Universal self. The muni khand or Yajnavalkya is a debate which goes on to give the philosophical backing to the earlier teaching. The Khila khand tackles various rituals of worship and meditation.
This Upanishad is a part of the Sama-Veda (see The Vedas). The name comes from the singer of the songs (samans) who is called Chandoga. The initial chapters of the Upanishad, discuss the ritual of sacrifice. The others debate the origin and profundity of the concept of Om, among other things.
This one forms part of the Rig-Veda. The purpose is to make the reader understand the deeper meaning of sacrifice and to take him away from the outer trappings of the actual act.
A part of the Yajur-Veda, this Upanishad is divided into three sections or vallis. The siksa valli deals with the phonetics of the chants, while the others, brahmananda valli and bhrgu valli deal with self-realization.
Also called the Isavasya Upanishad, this book deals with the union of God, the world, being and becoming. The stress is on the Absolute in relation with the world (paramesvara). The gist of the teachings is that a person's worldly and otherworldly goals need not necessarily be opposed to each other.
The name of this Upanishad comes from the first word kena, or by whom. It has two sections of prose and two of poetry. The verses deal with the supreme spirit or the absolute principle (brahmaana) and the prose talks of ishvara (god). The moral of the story is that the knowledge of ishvara reveals the way to self-realization.
Also called the Kathakopanishad, this Upanishad uses a story (katha) involving a young Brahmin boy called Nachiketa to reveal the truths of this world and the other beyond the veil.
Prashna literally means question, and this book is part of the Athrava-Veda. It addresses questions pertaining to the ultimate cause, the power of Om, relation of the supreme to the constituents of the world.
This book also belongs to the Atharva-Veda. The name is derived from 'mund' or to shave, meaning that anyone who understands the Upanishads is s(h)aved from ignorance. This book inscribes the importance of knowing the supreme brahmaana, only by which knowledge can one attain self-realization.
The Mandukya is an exquisite treatise which expounds on the principle of Om and its metaphysical significance in various states of being, waking, dream and the dreamless sleep. The subtlest and most profound of the Upanishads, it is said that this alone will lead one to the path of enlightenment.
The name of this Upanishad is after its teacher. It comments on the unity of the souls and the world in one all-encompassing reality. The concept of there being one god is also talked about here. It is dedicated to Rudra, the storm god.
Kausitaki Brahmana Upanishad
The Upanishad has come down to us in bits here and pieces there. The core of the text is dedicated to illustrating the fact that the path to release is through knowledge.
This is a comparatively later Upanishad as it has references to the Trinity of Hindu Gods (Shiva, Vishnu and Brahma) which is a later development, and plus references to the world being illusory in character reflects Buddhist influence.
Belonging to the Yajur-Veda, this Upanishad puts down a dialogue between the sage Subala and Brahma the creator of the Hindu Trinity of Gods. It discusses the universe and the absolute.
Belonging to the Athrav-Ved this Upanishad addresses some questions pertaining to renunciation.
The Paingala is again a dialog, this between Yagnavalky, the sage mentioned the Brhad-aranyaka's muni khanda and Paingalaa, a student of his. It discusses meditation and its effects.
This Upanishad delves into the state of kaivalya or being alone.
Belonging to the Saam-Veda the Vajrasucika reflects on the nature of the Supreme Being.