Evolution of the Vedic Schools of Thought: One of the most ancient and long enduring theological systems is found in the Indian subcontinent. Such theology, modern Hinduism, is the offspring of a merging of [1] a foreign religious system, the Vedic philosophy of the Aryans, brought by military force into the Indus valley between 2500 to 2000 BCE and [2] an indigenous religion which has never been fully deciphered. Evidence of a merging of the invading and indigenous schools of thought is found in the earliest religious literature of the subcontinent.

The oldest extant religious text in the Indo-European language is the Aryan Rig-Veda, composed in north-western India between 1500 – 1200 BCE; a religious text still in use with the Brahmins. The Rig-Veda begins with a small book addressed to the Aryan deities Agni, Indra and other gods, all arranged according to decreasing total number of hymns in each deity collection; for each deity series the hymns progress from longer to shorter ones; yet, the number of hymns per book increases. In terms of substance, the hymns predominantly discuss cosmology and praise deities in the earliest composed eight books, shifting in books 1 and 10, that were added last, to philosophical or speculative questions about the origin of the universe and the nature of god, the virtue of Dāna (charity) in society, and other metaphysical issues in its hymns.

About 600 years later, the first Upanishads appeared – apparently, an evolutionary modification of the original Vedic thought, as each Upanishad is associated with one of the four Vedas—Rig-Veda, Sama-Veda, Yajur-Veda (there are two primary versions or Samhitas of the Yajur-Veda: Shukla Yajur-Veda, Krishna Yajur-Veda), and Atharva-Veda. 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 Upanishads.

As we shall see, the primary additions to the Vedic system being the introduction of three underlying principles, Brahman, Atman, and Maya.

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 physical ritual and sacrifice. To a proponent of the Upanishads, anyone worshiping a divinity (other than Brahman or Atman) is considered a domestic animal of the gods (see the Brihadaranyaka Upanishad). 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.

The Kaushitaki Upanishad asserts that “external Vedic rituals offered in the morning and in the evening, must be replaced with inner rituals of introspection.” Not rituals, but, knowledge should be one’s highest 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 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.

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. It states that the over-lordship of the earth may be acquired by sacrificing a horse. It then goes on to say that spiritual autonomy can only be achieved by renouncing the universe which is conceived in the image of a horse.

In similar fashion, Vedic gods such as the Agni, Aditya, Indra, Rudra, Visnu, Brahma and others become equated in the Upanishads to the supreme, immortal and incorporeal Brahman-Atman of the Upanishads, god becomes synonymous with Self, and is declared to be everywhere, inmost being of each human being and within every living creature. The one reality or ekam sat of the Vedas becomes the ekam eva advitiyam or “the one and only and sans a second” in the Upanishads. Brahman-Atman and Self-realization develops, in the Upanishad, as the means to moksha (liberation, freedom in this life or after-life).

Two words of paramount importance in grasping the Upanishads are Brahman and Atman. The Brahman is the ultimate reality and the Atman is the One Self. Brahman is “the infinite Spirit Source and fabric and core and destiny of all existence, both manifested and unmanifested and the formless infinite substratum and from whom the universe has grown”. Brahman is the ultimate, both transcendent and immanent, the absolute infinite existence, the sum total of all that ever is, was, or shall be.

The word Atman means the immortal Perfect Spirit animating all living creatures, including animals and trees. Ātman is a central idea in all the Upanishads, and “Know your Ātman” their thematic focus. These texts state that the inmost core animating every person is not the body, nor the mind, nor the ego, but Atman – “Soul” or “Self”. Atman is the undivided spiritual essence in all creatures, their real innermost essential being. It is eternal, it is the essence, it is ageless. Atman is that which one is at the deepest level of one’s existence.

Atman is the predominantly discussed topic in the Upanishads, but they express two distinct, somewhat divergent themes. Some state that Brahman (Highest Reality, Universal Principle, Being-Consciousness-Bliss) is identical with Atman, while others state Atman is part of Brahman but not identical. This ancient debate flowered into various dual, non-dual theories in Hinduism. The Brahmasutra by Badarayana (~ 100 BCE) synthesized and unified these somewhat conflicting theories, stating 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.

The idea put forth by the Upanishadic seers that Atman and Brahman are One and the same is one of the most subtle theological contributions created by the imagination of men.

Two different types of the non-dual Brahman-Atman are presented in the Upanishads, according to Mahadevan. The one in which the non-dual Brahman-Atman is the all inclusive ground of the universe and another in which empirical, changing universe is a form of Maya, often translated as “illusion”.

The Upanishads describe the universe, and the human experience, as an interplay of Purusha (the eternal, unchanging principles, consciousness) and Prakti (the temporary, changing material world, nature). The former manifests itself as Ātman (Soul, Self), and the latter as Māyā. The Upanishads 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).

The term Maya [in the Upanishads] has been translated as ‘illusion,’ but then it does not concern normal illusion. Here ‘illusion’ does not mean that the world is not real and simply a figment of the human imagination. Maya means that the world is not as it seems; the world that one experiences is misleading as far as its true nature is concerned.” Māyā not only deceives people about the things they think they know; more basically, it limits their knowledge.”

In the Upanishads, Māyā is the perceived changing reality and it co-exists with Brahman which is the hidden true reality. Maya, or “illusion”, is an important idea in the Upanishads, because the texts assert that in the human pursuit of blissful and liberating Self-knowledge, it is Maya which obscures, confuses and distracts an individual.