Among the 40 odd commentaries on the Anusasana Parvan, Sankara's is the first. Incidentally this is also Sankara's first ever commentary (under Govind Acharya's tutelage). While Sankara provides the advaitic stand point, Parasara Bhatta, a disciple of Ramanuja provides the Vishitadvaitha stand point with heavy counter arguments against the initial theory. Parasara's work is called BhagavadGunaDarpana. Sri Satyasandha Yatiswara provides the Dvaita commentary for the same episode. This post is my understanding of the scripture after reading the analysis of Vishnu Sahasranama Bhashya of Parasara Bhatta by Dr. S Padmanabhan in his doctoral thesis on Parasara Bhatta and his contribution to Vishishtadvaitha. Dr.Padmanabhan belongs to the Department of Sanskrit, University of Madras. BhagavadGunaDarpana is Parasara's life's work. Apart from this Parasara Bhatta is reputed to have written 5 master pieces on various aspects of God. This post focuses mainly on his Vishnu Sahasranama bhashya (commentary). While Sankara's work came about in the 6/7th century, it is difficult to place Parasara's works. Dr. Padmanabhan places it approximately after Ramanuja's passing away(1137) in the 12th century. Anyway moving on to the actualy commentary....
Vaishyampayana, Dhrithirashtra's narrator says -- "Yudhishtira , a righteous man(dharmana) asks Bheeshma (shaantanavam) 6 questions". Here, Parasara notes that Bheeshma interestingly replies to these questions in more or less reverse order. The 6 questions are -
Kimekam daivatham loke kim vapyekam parayanam
Sthuvantha kam kamarchanta prapnuyur manava shubam
Ko dharma sarva dharmanam bhavatha paramo mathaha
Kim japan muchyathé janthur janma samsara bandhanath
1) The first question without specifying any deity asks "Who(kim) is the supreme(ekam) deity(daivatam) in the world" ?
2) The second question talks about the supreme value/abode (parayaanam) for a man to pursue.
3) Parasara believes the third question asks for the easy means to acheive the highest goal. ( Whom should I praise (sthuvanthan)?)
4) The fourth question asks for the more difficult means to acheive the same goal. (Whom should I worship (archantaah)?)
5) The fifth question is - What is the highest heaven/fullest conception of an ideal endeavour/virtue for a man to pursue?
6) What is the proper japa and whom should it be directed at to release us from material bondage (bandanaath)?
Bheeshma Picks up the last question of Yudhishtira and says "according to me - he who praises the Lord with the 1000 names is above all others. The answer to the second question is given next - The object of worship is Purushottama (Krishna) - the highest being who can be approached through meditation, praise and adoration. While commenting on this answer, Parasara is the only commentator to talk about "anuraga" (pure love) to attain god. Bheeshma then answers the 5th question saying " in my considered view worshipping Lord Vishnu is the highest virtue for a man to pursue". Here Parasara brings out the meaning Bhaktiyoga by using quotations from other older works. Bheeshma then answers the other two questions saying that - attaining Lord Vishnu, the Brahman (word, unrelated to the caste - brahmins) of the Upanishads is the highest goal in life. The nature of Vishnu is explained by Bheeshma in brief as the sole cause of creation, maintenance and destruction of the universe. Bheeshma then re-iterates that the repitition of these 1000 names of the deity purifies one from all sins and removes sorrow.
Parasara seems to be an expert in etymology and seems to be capable of providing (while not actually doing so) 4 -5 meanings for each of the 1000 names. He also seems to have explained wonderfully what Bheeshma calls gaunani (derived from qualities and actions of the Lord) and vikhyatani (well known). It is important to note that any commentary on the prasthana-traya (Vedas, Upanishads and the Gita) and related works like the Sahasranama are always means to an end. Every commentator finds a pattern in these texts that supports his hypothesis of what/who god is and means of reaching god. The hypothesis that has least number of contradictions or vedic violations is an accepted hypothesis. Apart from providing the commentary, Parasara spends a lot of time arguing against the advaitic viewpoints on nirguna and saguna Brahman. He argues extensively that chanting the 1000 names could be a "higher" means to attain god and not necessarily a "lower" means to attain god. He lists the flaws on removal of avidhya that he notes while quoting evidences form various puranas. I am a fan of analogies and Parasara's use of spider and the web to explain material/effective cause & effect was very interesting (the Lord(spider) is the cause and we(web) is the effect. The web later dissolves by the spider's own saliva). His insistence on there being only one material and effective cause makes sense but at the same time difficult to follow. Most of the thesis (which has been released as a book by the Vishitadvaitha research center) is tough to follow. The English is complex ( I mean really complex when they start talking about sentinent and non-sentinent entities) and refers to many concepts in the Gita that were beyond me. While a basic introduction to bhakti yoga, the vedantha concepts would help to understand this book, it does not help all the way.
I am still very naescent on Vedanthic readings. However, from reading an English transalation of Githartha Sangraha (where Yamuna Muni introduces Vishitadvaitha for the first time) and an analysis of Parasara Bhatta's works - it seems to me that man began his quest for God from the days of Yudhishtira. Sankara, Ramanuja, Desika and Madhvachariyar have proposed theories, which I feel are much similar to the scientific theories on gravity, relativity, atomic model etc. Each person proposes a theory and the next generation constantly refines, corrects and develops on that (its just my feeling. I know that many needn't share this).