The Upanishads (उपनिषद्) are late Vedic Sanskrit texts that supplied the basis of later Hindu philosophy. They are the most recent part of the Vedas, the oldest scriptures of Hinduism, and deal with meditation, philosophy, consciousness, and ontological knowledge. Earlier parts of the Vedas deal with mantras, benedictions, rituals, ceremonies, and sacrifices. While among the most important literature in the history of Indian religions and culture, the Upanishads document a wide variety of “rites, incarnations, and esoteric knowledge” departing from Vedic ritualism and interpreted in various ways in the later commentarial traditions. 

Aim of Upanishads

The aim of all Upanishads is to investigate the nature of Ātman (self), and “direct[ing] the enquirer toward it.” Various ideas about the relation between Atman and Brahman can be found, and later commentators tried to harmonize this diversity. 

Upanishads Etymology

The Sanskrit term Upaniṣad (from upa “by” and ni-ṣad “sit down”) translates to “sitting down near”, referring to the student sitting down near the teacher while receiving spiritual knowledge.(Gurumukh) Other dictionary meanings include “esoteric doctrine” and “secret doctrine”. Monier-Williams‘ Sanskrit Dictionary notes – “According to native authorities, Upanishad means setting to rest ignorance by revealing the knowledge of the supreme spirit.”

Adi Shankaracharya explains in his commentary on the Kaṭha and Brihadaranyaka Upanishad that the word means Ātmavidyā, that is, “knowledge of the self”, or Brahmavidyā “knowledge of Brahma”. The word appears in the verses of many Upanishads, such as the fourth verse of the 13th volume in the first chapter of the Chandogya Upanishad. Max Müller, as well as Paul Deussen, translate the word Upanishad in these verses as “secret doctrine”, Robert Hume translates it as “mystic meaning”, while Patrick Olivelle translates it as “hidden connections”.

Upanishads Development

Authorship of Upanishads

The authorship of most Upanishads is unknown. Radhakrishnan states, “almost all the early literature of India was anonymous, we do not know the names of the authors of the Upanishads”. The ancient Upanishads are embedded in the Vedas, the oldest of Hinduism’s religious scriptures.

Some traditionally consider being apauruṣeya, which means “not of a man, superhuman” and “impersonal, authorless”. The Vedic texts assert that they were skillfully created by Rishis (sages), after inspired creativity, just as a carpenter builds a chariot. The existing texts are believed to be the work of many authors.

Chronology of Upanishads

Scholars are uncertain about when the Upanishads were composed. The chronology of the early Upanishads is difficult to resolve, states philosopher and Sanskritist Stephen Phillips, because all opinions rest on scanty evidence and analysis of archaism, style and repetitions across texts, and are driven by assumptions about the likely evolution of ideas, and presumptions about which philosophy might have influenced which other Indian philosophies.

Indologist Patrick Olivelle says that “in spite of claims made by some, in reality, any dating of these documents [early Upanishads] that attempts a precision closer than a few centuries is as stable as a house of cards”.

Sanskrit Philologist and Indologist

Patrick Olivelle, a Sanskrit Philologist and Indologist, gives the following chronology for the early Upanishads, also called the Principal Upanishads:

• The Brhadaranyaka and the Chandogya are the two earliest Upanishads. They have edited texts, some of whose sources are much older than others. 
• The three other early prose Upanisads—Taittiriya, Aitareya, and Kausitaki come next; all are probably pre-Buddhist and can be assigned to the 6th to 5th centuries BCE.
• The Kena is the oldest of the verse Upanisads followed by probably the Katha, Isa, Svetasvatara, and Mundaka. All these Upanisads were composed probably in the last few centuries BCE. According to Olivelle, “All exhibit strong theistic tendencies and are probably the earliest literary products of the theistic tradition, whose later literature includes the Bhagavad Gita and the Puranas.”
• The two late prose Upanisads, the Prasna, and the Mandukya cannot be much older than the beginning of the common era.

The later Upanishads, numbering about 95, also called minor Upanishads, are dated from the late 1st-millennium BCE to mid-2nd-millennium CE. Gavin Flood dates many of the 20 Yoga Upanishads to be probably from the 100 BCE to 300 CE period. Patrick Olivelle and other scholars date 7 of the 20 Sannyasa Upanishads to likely have been completed sometime between the last centuries of the 1st millennium BCE to 300 CE. About half of the Sannyasa Upanishads were likely composed in the 14th- to 15th century CE.

Geography of Upanishads

The geographical center of ancient Brahmanism, comprising the regions of Kuru-Panchala, and Kosala-Videha together with the areas immediately to the south and west of these. This region covers:

• Modern Bihar,
• Nepal,
• Uttar Pradesh,
• Uttarakhand,
• Himachal Pradesh,
• Haryana,
• Eastern Rajasthan, and
• Northern Madhya Pradesh.

However, in the fourth chapter of the Kaushitaki Upanishad, a location named Kashi (modern Varanasi) is mentioned.

Upanishads Classification

Muktika canon: Major and minor Upanishads

There are more than 200 known Upanishads, one of which, the Muktikā Upanishad, predates 1656 CE and contains a list of 108 canonical Upanishads, including itself as the last. These are further divided into Upanishads associated with Shaktism (goddess Shakti), Sannyasa (renunciation, monastic life), Shaivism (God Shiva), Vaishnavism (God Vishnu), Yoga, and Sāmānya (general, sometimes referred to as Samanya-Vedanta).

Some of the Upanishads are categorized as “sectarian” since they present their ideas through a particular God or Goddess of a specific Hindu tradition such as Vishnu, Shiva, Shakti, or a combination of these such as the Skanda Upanishad. These traditions sought to link their texts as Vedic, by asserting their texts to be an Upanishad, thereby a Śhruti. Most of these sectarian Upanishads, for example, the Rudrahridaya Upanishad and the Mahanarayana Upanishad, assert that all the Hindu Gods and Goddesses are the same, all an aspect and manifestation of Brahman, the Vedic concept for metaphysical ultimate reality before and after the creation of the Universe.

Principal Upanishads

Of the early periods are the Brihadaranyaka and the Chandogya, the oldest upanishads.

The Aitareya, Kauṣītaki, and Taittirīya Upanishads may date to as early as the mid-1st millennium BCE, while the remnant date from between roughly the 4th to 1st centuries BCE, roughly contemporary with the earliest portions of the Sanskrit epics. Each of the principal Upanishads can be associated with one of the schools of exegesis of the four Vedas (shakhas). As a result, they are not difficult to comprehend for the modern reader:

New Upanishads

In 1908, for example, four previously unknown Upanishads were discovered in newly found manuscripts, and these were named Bashkala, Chhagaleya, Arsheya, and Saunaka, by Friedrich Schrader, who attributed them to the first prose period of the Upanishads. The text of three of them, namely the Chhagaleya, Arsheya, and Saunaka, were incomplete and inconsistent, likely poorly maintained or corrupted.

The main Shakta Upanishads, for example, mainly discuss doctrinal and interpretative differences between the two principal sects of a major Tantric form of Shaktism called Shri Vidya Upasana. The many extant lists of authentic Shakta Upaniṣads vary, reflecting the sect of their compilers, so that they yield no evidence of their “location” in Tantric tradition, impeding correct interpretation. The Tantra content of these texts also weakens its identity as a Upaniṣad for non-Tantrikas. 

Association of Upanishads with Vedas

All Upanishads are associated with one of the four Vedas—Rigveda, Samaveda, Yajurveda (there are two primary versions or Samhitas of the Yajurveda: Shukla Yajurveda, Krishna Yajurveda), and Atharvaveda. During the modern era, the ancient Upanishads that were embedded texts in the Vedas were detached from the Brahmana and Aranyaka layers of Vedic text, compiled into separate texts, and these were then gathered into anthologies of the Upanishads. 

These lists associated each Upanishad with one of the four Vedas, many such lists exist, and these lists are inconsistent across India in terms of which Upanishads are included and how the newer Upanishads are assigned to the ancient Vedas. In south India, the collected list based on Muktika Upanishad, published in the Telugu language, became the most common by the 19th century and this is a list of 108 Upanishads. In north India, a list of 52 Upanishads has been most common.

Upanishads Philosophy

The Maitri is one of the Upanishads that inclines more toward dualism, thus grounding classical Samkhya and Yoga schools of Hinduism, in contrast to the non-dualistic Upanishads at the foundation of its Vedanta school. They contain a plurality of ideas.

The Upanishads include sections on philosophical theories that have been at the foundation of Indian traditions. For example, the Chandogya Upanishad includes one of the earliest known declarations of Ahimsa (non-violence) as an ethical precept. Discussion of other ethical premises such as:

• Damah (temperance, self-restraint), 
• Satya (truthfulness), 
• Dāna (charity), 
• Ārjava (non-hypocrisy), and
• Daya (compassion).

Similarly, the Karma doctrine is presented in the Brihadaranyaka Upanishad, which is the oldest Upanishad.

Development of thought

The older Upanishads

While the hymns of the Vedas emphasize rituals and the Brahmanas serve as a liturgical manual for those Vedic rituals, the spirit of the Upanishads is inherently opposed to ritual. The older Upanishads launch attacks of increasing intensity on the ritual.

The Chāndogya Upanishad parodies those who indulge in the acts of sacrifice by comparing them with a procession of dogs chanting Om! Let’s eat. Om! Let’s drink.

Kaushitaki Upanishad

The Kaushitaki Upanishad asserts that “external rituals such as Agnihotra offered in the morning and in the evening, must be replaced with inner Agnihotra, the ritual of introspection”, and that “not rituals, but knowledge should be one’s pursuit”. The Mundaka Upanishad declares how man has been called upon, promised benefits for, scared unto, and misled into performing sacrifices, oblations, and pious works. 

Mundaka Upanishads

Mundaka thereafter asserts this is foolish and frail, by those who encourage it and those who follow it, because it makes no difference to man’s current life and after-life, it is like blind men leading the blind, it is a mark of conceit and vain knowledge, ignorant inertia like that of children, a futile useless practice. 

Maitri Upanishads

The Maitri Upanishad states:

The performance of all the sacrifices, described in the Maitrayana-Brahmana, is to lead up in the end to a knowledge of Brahman, to prepare a man for meditation. Therefore, let such man, after he has laid those fires, meditate on the Self, to become complete and perfect. — Maitri Upanishad

The opposition to the ritual is not explicit in the oldest Upanishads. On occasions, the Upanishads extend the task of the Aranyakas by making the ritual allegorical and giving it a philosophical meaning. For example, the Brihadaranyaka interprets the practice of horse sacrifice or Ashvamedha allegorically. 

Vedic Gods

In a similar fashion, Vedic Gods such as the Agni, Aditya, Indra, Rudra, Visnu, Brahma, and others become equated to the supreme, immortal, and incorporeal Brahman-Atman of the Upanishads. 

The one reality or ekam sat of the Vedas becomes the ekam Eva advitiyam or “the one and only and sans a second”. Brahman-Atman and self-realization develop, in the Upanishad, as the means to moksha (liberation; freedom in this life or after-life).

Upanishad categories

One group, which includes early Upanishads along with some middle and late Upanishads, was composed of metaphysicians who used rational arguments and empirical experience to formulate their speculations and philosophical premises.

The second group includes many middle and later Upanishads, where authors professed theories based on yoga and personal experiences. Yoga philosophy and practice, adds Jayatilleke, is “not entirely absent in the Early Upanishads”.

Brahman and Atman

Two concepts that are of paramount importance in the Upanishads are Brahman and Atman. The word Atman means the inner self, the soul, the immortal spirit in an individual, and all living beings including animals and trees. 

The Brahman is the ultimate reality and the Atman is the individual self (soul). Brahman is the material, efficient, formal, and final cause of all that exists. 

Pervasive, genderless, infinite, eternal truth

It is the pervasive, genderless, infinite, eternal truth and bliss which does not change, yet is the cause of all changes. Brahman is “the infinite source, fabric, core and destiny of all existence, both manifested and unmanifested, the formless infinite substratum and from which the universe has grown”.

Brahman in Hinduism, states Paul Deussen, is the “creative principle which lies realized in the whole world”. According to Koller, the Brahman sutras state that Atman and Brahman are different in some respects, particularly during the state of ignorance, but at the deepest level and in the state of self-realization, Atman and Brahman are identical, non-different. 

Reality and Maya

They describe the universe, and the human experience, as an interplay of Purusha (the eternal, unchanging principles, consciousness) and Prakṛiti (the temporary, changing material world, nature).

The former manifests itself as Ātman (soul, self), and the latter as Māyā. They refer to the knowledge of Atman as “true knowledge” (Vidya), and the knowledge of Maya as “not true knowledge” (Avidya, Nescience, lack of awareness, lack of true knowledge).

Schools of Vedanta

The Upanishads form one of the three main sources for all schools of Vedanta, together with the Bhagavad Gita and the Brahmasutras. Due to the wide variety of philosophical teachings contained, various interpretations could be grounded on the Upanishads. The schools of Vedānta seek to answer questions about the relation between atman and Brahman, and the relation between Brahman and the world. The schools of Vedanta are named after the relationship they see between atman and Brahman:

• According to Advaita Vedanta, there is no difference.
• According to Vishishtadvaita, the jīvātman is a part of Brahman and hence is similar, but not identical.
• According to Dvaita, all individual souls (jīvātmans) and matter as eternal and mutually separate entities.

Other schools of Vedanta include Nimbarka’s Dvaitadvaita, Vallabha’s Suddhadvaita, and Chaitanya’s Acintya Bhedabheda. The philosopher Adi Sankara has provided commentaries on 11 mukhya Upanishads.

Advaita Vedanta

Advaita literally means non-duality, and it is a monistic system of thought. It deals with the non-dual nature of Brahman and Atman. Gaudapada was the first person to expound on the basic principles of the Advaita philosophy in a commentary on the conflicting statements of the Upanishads. 

Shankara in his discussions of the Advaita Vedanta philosophy referred to the early Upanishads to explain the key difference between Hinduism and Buddhism, stating that Hinduism asserts that Atman (soul, self) exists, whereas Buddhism asserts that there is no soul, no self.

Mahāvākyas (Great Sayings)

• “Prajñānam Brahma” – “Consciousness is Brahman” (Aitareya Upanishad)
• “Aham brahmāsmi” – “I am Brahman” (Brihadaranyaka Upanishad)
• “Tat tvam asi” – “That Thou art” (Chandogya Upanishad)
• “Ayamātmā brahma” – “This Atman is Brahman” (Mandukya Upanishad)

Vishishtadvaita

Sri Ramanuja disagreed with Adi Shankara and the Advaita school. Visistadvaita is a synthetic philosophy bridging the monistic Advaita and theistic Dvaita systems of Vedanta. Sri Ramanuja frequently cited the Upanishads and stated that Vishishtadvaita is grounded in it.

The school recommends devotion to godliness and constant remembrance of the beauty and love of personal God. This ultimately leads one to the oneness with abstract Brahman. The Brahman is a living reality, states Fowler, and “the Atman of all things and all beings” in Sri Ramanuja’s interpretation.

Dvaita

Madhvacharya, much like Adi Shankara’s claims for Advaita, and Sri Ramanuja’s claims for Vishishtadvaita, states that his theistic Dvaita Vedanta.

According to the Dvaita school, states Fowler, the “Upanishads that speak of the soul as Brahman, speak of resemblance and not identity”. Madhvacharya interprets their teachings of the self-becoming one with Brahman, as “entering into Brahman”, just like a drop enters an ocean. This to the Dvaita school implies duality and dependence, where Brahman and Atman are different realities. Brahman is a separate, independent, and supreme reality in the Upanishads, Atman only resembles Brahman in a limited, inferior, dependent manner according to Madhvacharya.

Reception in the West

The German philosopher Arthur Schopenhauer read the Latin translation and praised the Upanishads in his main work, The World as Will and Representation (1819), as well as in his Parerga and Paralipomena (1851). He found his own philosophy was in accord with the Upanishads, which taught that the individual is a manifestation of the one basis of reality. For Schopenhauer, that fundamentally real underlying unity is what we know in ourselves as “will”. Schopenhauer used to keep a copy of the Latin Oupnekhet by his side and commented,

In the whole world there is no study so beneficial and so elevating as that of the Upanishads. It has been the solace of my life, it will be the solace of my death.

Schopenhauer’s philosophy influenced many famous people and introduced them to the Upanishads. One of them was the Austrian Physicist Erwin Schrödinger, who once wrote:

“There is obviously only one alternative,” he wrote, “namely the unification of minds or consciousnesses. Their multiplicity is only apparent, in truth there is only one mind. This is the doctrine of the Upanishads.”