3rd Sutra of Brahma Sutra

शास्त्र योनित्वात्
Sastra Yonitwat.
Sastras (Scriptures) are the means of correct Knowledge.
This sutra is a continuation, support and confirmation of the earlier Sutra that Brahman being the primal cause of the world is known only through the scriptures. Thus Brahman being the cause is not concluded by means of any analogy, estimation or inference, but, is supported by the Scriptures which are but the first hand realization of the Seers of truth. This also documents that the Srutis alone are the evidence of the existence of Brahman.
Now, the objection that has been raised was- "Brahman is an already existing entity like the pot etc and thus it can be known by other means of right knowledge also other than the scriptures."
Answer: There are enough scriptural texts that testifies that Brahman is beyond comprehension and is not the object of knowledge perceptible unlike the pot etc. Any object which has a form, name, taste, smell etc can be defined by other means apart from the scriptures. For example, in the first chapter of keno Upanishads it says thus-
अन्यदेव तद्विदितादथो अविदितादधि ।
इतिशुस्रुम पूर्वेषां ये नस्तद्व्यचचक्सिरे।।
(That Brahman is definitely unlike the one that is Known, and again, its beyond the unknown. Such are the utterances that we had heard of the ancient sages who explained the same to us).
Keno Upanishad keeps on repeating the same characteristic of Brahman being non perceivable to the different sense organs, the mind and the Prana( the five vital forces). Similar facts has been echoed in the Brhadaranyaka as- "He who controls the organ of speech from within" Br. III. vii 17. Or, in the Chandogya as, " One only; without a second", VI.ii.1 and "Where one doesn't see anything else", VII,xxiv.1. " Hence, the finite is that where one sees something else" Ch. VII.xxiv.1. Thus, an object which is completely non perceptible through direct experiences of the senses and mind, intellect etc, cannot be established by inference and analogy. Therefore it can be known only through the scriptures. Earlier we had discussed, "One who is ignorant of the Scriptures cannot have right knowledge of the Brahman." The other means of knowledge does have a scope but only when Brahman is established. They might be supplementary, not independent.

Topics of the Brahma Sutras

Before going into the detailed study of the Sutras, we should learn something about "Adhikaran" or topic. The literal meaning of topic is the subject discussed. For example, in the 1st Sutras the word Jignasa or questioning was widely used and the subject matter also was about questioning. Thus the 1st Aphorism is called "Jignasa Adhikaran". This topic consists of only one sutra. Similarly, the 2nd, 3rd and 4th sutras are also of independent topic and their naming has been done with respect to the subject discussed. In other topics, there are more than one sutras. There is an arithmetic arrangement in the no. of sutras and its topics.
Brahma Sutras are called the 'Uttar Mimansha' because of the fact that they talk about Brahman being the only object of knowledge and attainment unlike the "Purva Mimansha" where attainment of heaven is the prime objective. According to Sankara, there are in all 555 sutras and 191 "Adhikarana" or topics which are divided into 4 adhyaya or sections and each section into 4 padas or sub sections.
The topic consists of 5 basic points viz. 1) the subject; 2) confusion raised; 3) justification of confusion with reference to the Shruti; 4) justification against the confusion with reference to Shrutis; 5) Conclusion. To derive the actual essence of the sutras, these five basic points have to be discussed in details and without the same, the conclusion derived will be considered invalid.
Brahma Sutras are the testimony and explanation of the Upanishads. Thus, in each topic, the definite meaning of the Shruti is discussed. Those words of the Shrutis are the topic heads of the respective topics in the Brahma Sutras.

The theory of Adhyasa in the Brahma Sutras

( It is our pleasure to present this short note on Adhyasa on the eve of the Guru Purnima. Guru Purnima marks the birth Anniversary of Veda Vyasa or Badarayana who is also considered to be the author of Brahma Sutras along with Mahabharata, the 18 Puranas, Bhagavat Gita and Adyatma Ramayana. He is also the first who had transcribed the Vedas.)
The essence of all scriptures is - एकं अद्वितियम नेहा नानास्ति किंचन - there is only one without a second. The Absolute existence is but One and that I am that. I am that One which is birth-less, changeless and ever Tranquil. The relation between the Individual soul and the Universal Soul in the Anubandhya Chatustaya is that the Jiva( individual soul) is undifferentiated from the Absolute Soul. The Upanishads states thus- तत त्वम् असी - thou art that.
Now, the question is, if the scriptures says so, why and how do we see this difference? How is that possible that such a variation is experienced as real in our day to day routine. We see that there is a complete contradiction to what the scriptures say and that what we experience though our senses in the material world. But, because truth is one, and if it is true, it cannot contradict experience.
To make things clearer, Sankara documented the theory of Adhyasa or super imposition before commencing into the commentary of the Brahma Sutras. According to Him, this deviation of experience or the duality is due to Maya or illusion. In the waking, dreaming state etc though we see this plurality yet it disappears once the real Knowledge is manifested. This wrong perception is due to the effect of Maya or ignorance. The moment the Self is being associated with the waking, dreaming and the sleeping state and an obvious consequence of association with its experiences as our own, the Self appears to be an individual entity. The cause of all duality is because of the ignorance in identifying the Real from the unreal and as a result seems to be connected with the qualifications or Adjuncts viz. The body, senses mind etc. Body, senses, mind, intellect or the ego are but impositions on the attribute less Self which is without any adjuncts. This unreal association of the Self makes it appear to be the doer or the enjoyer whereas the fact is- it is always beyond. Being immortal and birth less, it appears to be going through birth and death, being attribute less, it appears to have qualities and enjoy the happiness and suffer the miseries of the material world.
Brahma Satya Jagad Mithya, Jiva Brahmaiva Na Parah.
This is how Sankara explains the phenomenon of super imposition. Mithya is a word which doesn't imply to something which is non- existent. Mithya is referred to something which does exists but cannot be correctly identified. Like the famous example of the Advaita Vedanta regarding the rope and the snake. Here rope is the real existence and snake is super imposed on the rope. When I see the super imposed snake, though snake is unreal but its existence depends upon the existence of the real rope. Hence, by the right knowledge of the snake, we can come across the Knowledge of the reality, here, the rope. Hence, due to super imposition or Adhyasa, the Self is identified to be having name and form.
Therefore, we can easily come to the conclusion that the identification of the Self with the body,mind,intellect etc is only due to the superimposition or Adhyasa. All the miseries of finiteness and relativity starts with the perception that I am the body, mind etc. Our birth, death etc are all but due to this false notion. Because of Adhyasa, one though omniscient, omnipotent and omnipresent seems to be bounded by the strings of time, space and causation. Hence, the only way to get liberated from the mundane existence is to get rid of the false notion of I through true knowledge. The knowledge of oneness with the Absolute is the only way to pass beyond death and miseries. As the upanishads declare - ( Asabdam Asparsham Arupam Avyayam, Tatha Arasam..........Nicayya Tat Mrtyumukhat Pramucyate) - one becomes free from the jaws of death by knowing the one that is soundless, touchless, formless, undiminishing and tasteless.
When the Self is realized, the phenomenal world disappears instantly. When by listening to the Mahavakyas from the Guru and then engaged into the inquiry of the Self through comprehension and discrimination, one realizes the Self, He goes beyond all modifications or superimpositions. This reverse process by which we become one with our real nature leaving behind all the transitory existences is called Adhyaropa or Apavada. Thus Apavada is a process by which the existence of snake completely dilutes into the existence of rope and remains as a rope henceforth. The explanation of Sankara that the world is maya or illusion has given this philosophy the name of Mayavada or Anirvachaniya Khyativada( the doctrine of apparent modification of Brahman into the phenomenal world)