SIGNIFICANCE OF GURU

The necessity of a Guru
Shankara taught that access to Vedic texts, a prerequisite for liberation, should be restricted, in accordance with caste rules, to upper-caste Hindu males. He seems to have generally held that liberation can only be attained by a male renunciant of the Brahmin caste. According to Shankara and others, anyone seeking to follow the philosophy of advaita vedanta must also do so under the guidance of a Guru (teacher).
The Guru must have the following qualities (see Mundaka Upanishad 1.2.12):

1. Śrotriya — must be learned in the Vedic scriptures and sampradaya
2. Brahmaniṣṭha — literally meaning established in Brahman; must have realised the oneness of Brahman in everything and in himself

The seeker must serve the Guru and submit questions with all humility in order to remove all doubts (see Bhagavad Gita 4.34). By doing so, advaita says, the seeker will attain moksha (liberation from the cycle of births and deaths).
According to Adi Shankara, knowledge of brahman springs from inquiry into the words of the Upanishads, and the knowledge of brahman that shruti provides cannot be obtained in any other way. It is the teacher who through exegesis of shruti and skillful handling of words generates a hitherto unknown knowledge in the disciple. The teacher does not merely provide stimulus or suggestion.

See also: Guru-shishya tradition

 Sādhana Chatuṣṭaya

            Any mumukṣu (one seeking moksha) has to have the following four sampattis (qualifications), collectively called Sādhana Chatuṣṭaya Sampatti (the fourfold qualifications):

1. Nityānitya vastu viveka — The ability (viveka) to correctly discriminate between the eternal (nitya) substance (Brahman) and the substance that is transitory existence (anitya).
2. Ihāmutrārtha phala bhoga virāga — The renunciation (virāga) of enjoyments of objects (artha phala bhoga) in this world (iha) and the other worlds (amutra) like heaven etc.
3. Śamādi ṣatka sampatti — the sixfold qualities of śama (control of the antahkaraṇa^[8][9]), dama (the control of external sense organs), uparati (the refraining from actions; instead concentrating on meditation^{[citation needed]}), titikṣa (the tolerating of tāpatraya), śraddha (the faith in Guru and Vedas), samādhāna (the concentrating of the mind on God and Guru).
4. Mumukṣutva — The firm conviction that the nature of the world is misery and the intense longing for moksha (release from the cycle of births and deaths).

Adi Shankara states in Tattva bodha (1.2) that moksha, or liberation, is available only to those possessing the above-mentioned fourfold qualifications. Thus any seeker wishing to study advaita vedānta from a teacher must possess these.

Pramāṇas

Pramā, in Sanskrit, refers to the correct knowledge, arrived at by thorough reasoning, of any object. Pramāṇa (means of knowledge, Sanskrit) forms one part of a tripuṭi (trio), namely,

1. Pramātṛ, the subject; the knower of the knowledge
2. Pramāṇa, the cause or the means of the knowledge
3. Prameya, the object of knowledge

In Advaita Vedānta, the following pramāṇas are accepted:

• Pratyakṣa — the knowledge gained by means of the senses
• Anumāna — the knowledge gained by means of inference
• Upamāna — the knowledge gained by means of analogy
• Arthāpatti — the knowledge gained by superimposing  the known knowledge on an appearing knowledge that does not concur with the known knowledge
• Āgama — the knowledge gained by means of texts such as Vedas (also known as Āptavākya, Śabda pramāṇa)

Ontology
Kārya and kāraṇa
The kārya (effect) and kāraṇa (cause) form an important area for investigation in all the systems of Vedanta. Two kāraṇatvas (ways of being the cause) are recognised:

1. Nimitta kāraṇatva — Being the instrumental cause. For example, a potter is assigned Nimitta kāraṇatva as he acts as the maker of the pot and thus becomes the pot's instrumental cause.
2. Upādāna kāraṇatva — Being the material cause. For example, the mud is assigned Upādāna kāraṇatva as it acts as the material of the effect (the pot) and thus becomes the pot's material cause.

Advaita assigns Nimitta kāraṇatva to Brahman with the statements from the Vedas (only two are given below):

Sarvāṇi rūpāṇi vicitya dhīraḥ. Nāmāni kṛtvābhivadan yadāste — That Lord has created all the forms and is calling them by their names (Taitiiriya Aranyaka 3.12.7)

Sa īkṣata lokānnu sṛjā iti — He thought, "Let Me create the worlds" (Aitareya Upanishad^[10] 1.1.1)

Advaita also assigns Upādāna kāraṇatva to Brahman vide the statements from the Vedas (only two are given below):

Yathā somyaikena mṛtpinḍena sarvaṃ mṛnmayaṃ vijñātaṃ syādvācāraṃbhaṇaṃ vikāro nāmadheyaṃ mṛttiketyeva satyaṃ — Dear boy, just as through a single clod of clay all that is made of clay would become known, for all modifications is but name based upon words and the clay alone is real (Chandogya Upanishad 6.1.4)

Sokāmayata bahu syāṃ prajāyeti — (He thought) Let me be many, let me be born (Taittiriya Upanishad 2.6.4)

The Chandogya Upanishad 6.2.1 states

Ekamevādvitīyaṃ — It is One without a second

Thus, based on these and other statements found in the Vedas, Advaita concludes that Brahman is both the instrumental cause and the material cause