Nature of ajnyAna.
In the study of jagat and the jIva, we have understood that the names and forms of jagat as well as the jIva acting with an understanding of he is the body, mind or intellect are appearances only; in their svarUpa, they are identical with Brahman. The jIva is not aware that he is Brahman. This unawareness that he is Brahman is the avidya or ajnyAna of the jIva. This avidya leads him to misunderstand himself. This misunderstanding is adhyAsa - ajnyAna is the cause of adhyAsa. In other words, misunderstanding that he is, when he is not, is adhyAsa. The mis-understanding (projection or superposition) that he is the body - adhyAsa- , makes him experience pain and pleasure, happiness and sorrow etc., caused by the attachment to and fear from the multiplicity. This adhyAsa makes him imagine or conceive other bodies, material wealth etc. These he cannot create himself; these are created by Brahman by the power of mAyA, for the experience of karma of the jIva. In the absence of other bodies or material wealth, the jiva has no scope for the experience of karma. So the adhyAsa, created by avidya is supported by jagat (caused by the mAyA). In addition to supporting the birth and death cycle of the jIva, the jagat also supports jIva's quest for liberation through the practice of sAdhana chatuShTaya and shravaNa, manana and nidhidhyAsana.
avidya itself is not the culprit; but the adhyAsa arising out of avidya is the culprit - not knowing who he is (avidya), he conceives man woman, induced by desires (adhyAsa) moves from body to body. For example, not knowing (ajnyAna) there is a pit, is not dangerous by itself. But driven by some desire, going towards the pit (adhyAsa) could be dangerous. What this tells is that, the adhyAsa is of the 'bhAvarUpa'- of the form of 'is' in the antahkaraNa (wife is there, wealth is there etc.). The awareness in the misunderstanding is bhAvarUpa. But the kAraNa for this, the ajnyAna - lack of knowledge - is of the 'abhAvarUpa' - of the form of 'is not'. So the Atman does not have any relation to the kAraNa Sharira called ajnyAna (with the advent or dawn of jnyAna, the ajnyAna disappears). So the ajnyAna or avidya is not in the Atman. All that is in the Atman is bhAva rUpa - like pAramArthika satya. The vyAvahArika satya is bhAvarUpa of names and forms; the prAtbhAsika satya is bhAvarUpa of mirage. That which is opposed to all these and is really not in the Atman is abhAvarUpa; avidya belongs to this abhAvarUpa category.
How does bhAvarUpa adhyAsa come from abhAvarUpa ajnyAna? This is resolved when one notes that the ajnyAna as kArana of adhyAsa is a pretext, and not a nimitta or upAdAna. As an example, an abandoned house invites a homeless person to occupy the house. The abhAva of the owner did not create the homeless person (neither nimitta nor upAdAna). When the owner comes back to claim the house, the homeless person quits the place. In this example, the intellect of the ajnyAni is the abandoned house, and the jnyAna is the owner. When the jnyAna is realized (owner comes back), ajnyAna disappears (homeless person quits). That is why it was said that adhyAsa - awareness (he is body, intellect etc.) in ajnyAna - is bhAvarupa. Only because ajnyAna is abhAvarUpa, it can be totally eliminated. If it is of the bhAvarUpa, it cannot be totally eliminated when jnyAna takes over or then it has to find place in another jIva, which is absurd. The avidya induced (desire oriented) actions of current life begets next life; like wise the desire oriented actions of previous life(or lives) got us this life. The previous life was derived from its previous life etc. Therefore avidya is anAdi or beginning-less, spanning back to many previous kalpas. There is no beginning for avidya. If there were to be a beginning for avidya, that would be synonymous with Brahman loosing his svarUpa, jnyAna and Ananda and acquiring avidya. How can it be Brahman, if it were to loose its svarUpa? (Brahma satya). Therefore avidya is anAdi or beginning-less; however, the blessed situation is that avidya has an end - it is sAnta (sa anta), through vidya. avidya is an affliction with the jIva and not Brahman. Krishna tells Arjuna
"bahUnI me vyatItAni janmAni tava cha Arjuna
tAni aham vEda sarvaNi na tvam vEttha parantapa "
- Arjuna, we both have crossed many lives; I know all of them, but you don't know them - (gIta 4-5).
The jIva sheds avidya and realizes Brahman. Brahman cannot loose jnyAna and become jIva. vidya can be acquired and not lost. avidya can be lost and not acquired. Here we can recall a parable from Sri Ramakrishna. Some tigers came to attack a cow heard. The villagers came to protect their cow heard. In the scuffle, all tigers escaped, except a pregnant tiger that got tired, delivered the baby tiger and died. The villagers took custody of the baby tiger and looked after the baby tiger. It grew with the cow heard, and became a big tiger. One day when this tiger was grazing in the forest with other cattle, another forest tiger was surprised at this domesticated tiger grazing grass. The forest tiger came up to the domesticated tiger and said "what is wrong with you? You are a tiger! You should be attacking the cows, not graze with them". The domesticated tiger did not believe the forest tiger. The forest tiger took the domesticated tiger to the nearby pond and asked it to look at its image in the water. It then said, "what do you see in the image? A tiger face like me or a cattle face like them?". The domesticated tiger realized it is a tiger and not a cattle and went to the forest. The tiger shed its ajnyAna and realized its tiger-hood. However, it did not acquire ajnyAna and become a cattle (its ajnyAna only made it think it is a cattle). So Brahman cannot acquire ajnYana and become a jIva.
avidya-imagined or avidya-fabricated (avidya kalpita)
The witnessed names and forms as a result of avidya are abhAva rUpa like avidya itself. So the perception itself is avidya-fabricated. The jagat of names and forms is of the svarUpa of Brahman. This knowledge itself is vidya (jnyAna). Prior to this jnyAna, the Brahman was non-Brahman for our perception. So the names and forms were avidya-fabricated during avidya. When it was rejected, the non-brahman(ness) disappeared. With jnyAna, the names and forms don't disappear, but the attitude or spirit of understanding changes - seeing Brahman in its svarUpa and not the names and forms (seeing gold, while looking at the ornament). For example a married man has a wife, mother-in-law, brother-in-law etc. If the marriage is divorced, the above relations don't exist any more; however those people don't die and are still very much alive. The shruti describes jagat of names and forms by both descriptions - (1) at the kAraNa (causal) level, the jagat is Brahman; at the kArya (or effect) level, jagat is avidya-fabricated. The anAtma is fabricated by avidya and there is nothing apart from Atma.
Om shAntih, shAntih, shAntih (Om peace, peace, peace).