One of the six orthodox systems of Indian philosophy is Vedanta. The Vedanta philosophy is important both for its philosophical views and its close connections with the existing Hinduism. Uttara Mimamsa (also called Vedanta Sutra or Brahma Sutra) of Badarayana deals with the Brahman doctrine. It consists of 555 sutras. Vedanta bases its many observations and explanations on Samkhya system. Vedantist does not accept multiple Purushas; Reality is one as Brahman and the rest of the universe including mind and its modifications are but superimposition upon this one Reality.

The word Vedanta is a compound of veda "knowledge" and anta "end, conclusion", translating to "the culmination of the Vedas".

The Vedanta can be put as:
a) Absolute Monism of Shankara or Advaita: Shankara maintains that there exists but One Reality as Brahman whose nature is pure Consciousness. Shankara discusses the question of reality of individual soul, this world, and Ishwara from this point of view and labels them as illusory. Final Liberation comes when this knowledge of unity of individual soul and eternal Soul is established through meditation and samadhi, transcendental knowledge.

b) Vishishtha Advaita or qualified monism of Ramanuja: Ramanuja is the 11c AD founder of Vishista-advaita Vedanta. This is a philosophy of religion; and therefore it gives a synthetic view of the spiritual experiences of God or Brahman. It affirms the Upanishadic truth by realizing Brahman everything else is realized. Heavily depending upon theory of Karma, this philosophy applies the law of cause and effect to moral experiences.

The basic problem of Shankara`s philosophy is how such pure consciousness appears, in ordinary experience, to be individualized ("my consciousness") and to be of an object ("consciousness of blue"). Shankara regarded moral life as a necessary preliminary to metaphysical knowledge and thus laid down strict ethical conditions to be fulfilled by one who wants to study Vedanta. For him, however, the highest goal of life is to know the essential identity of his own self with Brahman, and though moral life may indirectly help in purifying the mind and intellect, over an extended period of time knowledge comes from following the long and arduous process.

The sub-schools of the Vedanta:
i) Advaita: This is one of the dominant sub-schools of the Vedanta theory. Advaita literally means non-dualism and is based on the Upanishads, Brahma Sutra and Bhagavad Gita. The word "Advaita" essentially refers to the identity of the Self (Atman) and the Whole (Brahman).

Advaita asserts that the real self (jiva) is Brahman who is nirguna (attribute-less), nishkriya (activity-less), nir-avayava (without parts) nirupadhika (unconditional absolute) and nirvisesha (simple, homogeneos entity). The world is a manifestation of this Brahman and hence much importance is given to the Upanishadic statements like tat tvam asi (thou art that) and aham brahmasmi (I am Brahman). Although the world according to Advaita is monistic the real world perceived by man is dual. This discrepancy is attributed to the presence of Maya (illusion, extraordinary and inexpleicable power) or Adhyasa (superimposition) and absence of knowledge.

Advaita also prescribes Yoga and Karma-sanyasa as the methods to achieve moksha. Advaita vedanta requires anyone seeking to study advaita vedanta to do so from a Guru (teacher). Adavaita also prescribes three levels of truth: The transcendental or the Paramarthika level in which Brahman is the only reality and nothing else; The pragmatic or the Vyavaharika level in which both Jiva (living creatures or individual souls) and Ishvara are true; and The apparent or the Prathibhasika level in which even material world reality is actually false.

ii) Visishtadvaita: This is a non-dualistic sub-school of Vedanta. VishishtAdvaita (literally "Advaita with vishishtam"), in which the Brahman alone exists, but is characterised by multiplicity. Ramanuja, the founder, maintained that God himself is composed of parts; individual souls and physical world comprise the body of God. Ramanuja unified a personal theist god with the single universal god of monism. This unification made the system popular among the common folk. Ramanuja proposed that the Prasthana Traya i.e. Upanisads, Bhagavad Gita, and Brahma Sutras are to be interpreted in way that shows this unity in diversity.

Ramanuja recognises three factors:
Achit: matter which has no conscious
Chit: Soul or those which have life and can experience
Ishvara: God

Chit and Achit are dependent on Ishvara. Chit, Achit and Ishvara are distinct but their organic unity is accepted.

This later came to be known as the Thathva, or one of the three principles of VishishtAdvaita. The other two being: Hitha, The means of realisation i.e. through Bhakti (devotion) and Prapatti (self-surrender) and PurushArtha, the goal to be attained i.e. moksha or liberation from bondage.

Ramanuja argues vehemently against understanding Brahman as one without attributes. Brahman is Nirguna in the sense that impure qualities do not touch it.

iii) Dvaita: It is also known as Tattvavada and Bheda-vada. It was founded by Madhvacharya. It stresses on a strict distinction between God (Vishnu) and the individual living beings (jivas). According to Madhvacharya, souls depend on God for their existence. God is seen as the cause of this universe and not of the material world. Accoring to him Brahmin is an attribute of God, i.e, Vishnu, "brahmashabdashcha vishhnaveva". Madhvacharya states that Vishnu is not just any other deity, but is rather the singular, all-important and supreme one. Vishnu is always the primary object of worship, and all others are regarded as subordinate to Him.

The Dvaita doctrine was summarized by Vyasa Tirtha as comprising nine tenets or prameyas.

Vishnu is accorded supreme status and Lakshmi is his consort. Brahma and Vayu come the next level with both on the same level. Their wives (Saraswati and Bharati) occupy the next level. Garuda, Sesha, Shiva, Indra, Kama, Surya, Chandra, Varuna, Nala, Vigneshand others occupy the succeedingly lower hierarchy.

According to Madhvacharya, life in this entire universe can be divided into two groups Kshara and Akshara. Kshara being life with destructible bodies while Akshara have indestructible bodies. Laxmi is Akshara while others from Brahma and so on are Ksharas or Jeevas.

Many of the doctrines in the Dvaita traditions resemble those of strict monotheism that is predominant amongst followers of Semitic religions. Dvaita provides a greater role to Bhakti than other schools of Vedanta. Followers of Dvaita believe in the supremacy of Vishnu over other deities including Shiva and do not believe in the Hindu concept of Trinity.

iv) Dvaitadvaita (Bhedabheda): The originator of this philosophy was Nimbarka, a 13th Century Vaishnava Philosopher. He believed in three catagories of of existence which are similar to VishishtAdvaita. These are the Chit, Achit and Isvara. Boht Chit and Achit have attributes (Guna) and capacities (Swabhaava), which are different from those of Isvara, who is the God, is independent and exists all by himself. Chit and Achit, both depend on Iswara. Therfore Isvara has independent existence and Chit and Achit have a dependent existence.

Isvar is the Brahman, the creator, the superior, and the controller of all. All beings arise from Him, nothing that is superior to Him. The Lord alone is the first cause, the manifestor of all names and forms, and none else. Nimbarka discusses two aspects of Brahman. On one hand, Brahman is eternal and great, the greatest of the great, the highest of the high, the creator, etc. of the Universe, high above the individual soul, of which He is the Lord and the ruler. But, on th e other aspect He is the abode of infinite beauty, bliss and tenderness, and in intimate connection with the soul.

Chit or Jiva or individual soul is of the nature of knowledge. The jiva is also ego (ahamarthah). This ego continues to persist not only in the state of deep sleep, but also in the state of liberation. The jiva is atomic in size; at the same time his attribute, knowledge, is omni-present.

Achit or jagat is of three different types: prakrta, aprakrta, and kala.Prakrta or Prakriti is the primal matter, is not the product of prakrti and its real nature is not clearly brought out.

v) Shuddhadvaita: According to Vallabhacharya (1479 - 1531), the founder of the Vallabha sect in the Indian philosophy, the glorious Krishna in His "sacchidananda" form is the Absolute Brahman. Krishna is believed to be permanently playing out His sport or Leela, from His seat. This is beyond the divine Vaikuntha, the abode of Vishnu and Satya-loka, the abode of Brahma the Creator, and Kailas, the abode of Shiva.

Eight disciples of Vallabhacharya are called the ashta-chaap (eight reprints). Foremost among them was Surdas, the blind poet of Agra. Others were Krushnadas, Paramanand, Kumbhandas, Chaturbhuj, Nanddas, Chhitswami, and Govinndas.

Bhakti is the only path to obtain this bliss of Lord Krishna. Pushti bhakti is recommended in this age and this path is called the `pushti maarg`.

There are nine forms of bhakti. Among them Atma-nivedana is one in which the body, heart and soul is given up to the cause of God. It is considered to be the fullest expression of what is known as Atma-nivedana (= giving-up of oneself).

vi) Acintya Bheda Abheda: Chaitanya Mahaprabhu (1486-1534), was a devotee of Lord Krishna. He was an ascetic Vaishnava monk and social reformer in 16th century Bengal. He proposed a synthesis between the monist and dualist philosophies by stating that the soul is both distinct and non-distinct from God. He identified this soul with Lord Krishna. He said that this philosophy maybe experienced through a process of loving devotion. The ISKCON temples of today, which are found all over the world, also known as the Hare Rama, Hare Krishna mandir, are based on this philosophy.