Did Shankara reject some doctrines of Atman or Brahman in order to reconcile Atman and Brahman?

Question

Natalia Isayeva's 1992 Shankara and Indian Philosophy, p. 2, says that Shankara was "the most brilliant personality in the history of Indian thought" and that because he united Atman and Brahman, he is to Indian thought what St. Thomas Aquinas, who reconciled Aristotelian philosophy with Christianity, is to Christian philosophy.

Is this comparison between Shankara and St. Thomas Aquinas fair?

St. Thomas, for example, rejected anything in Aristotelian thought that contradicted the Catholic faith (e.g., Aristotle thought, contrary to the Catholic faith, the world is eternal).

Did Shankara reject some doctrines of Atman or Brahman in order to reconcile Atman and Brahman?

Answer 1

Yes, Shankara explains away many scriptural passages that do not fit the Advaita Vedanta model. I am posting an excerpt of Sankara's introduction to his commentary of Svetasvatara Upanishad where he explains in detail his approach towards interpretation of Scripture.

The following objection may be raised: Granting that Brahman cannot have two aspects, because It is non-dual only, how can this prove that Brahman is devoid of forms? It may very well be endowed with the aspect of many forms.

In answer Vyasa contends (Brahma Sutra III.ii.14) that the conclusion of the scriptures is that Brahman is formless. This is because the scriptural passages describing the formlessness of Brahman reveal Its primary aspect.

To quote the scriptures: "It (Brahman) is neither gross nor subtle, neither short nor long; It is soundless, formless, and immutable."

"Akasa (matter) alone is the bearer of names and forms; that which is within them is Brahman." (Chandogya Upanishad VIII.xiv.1.)

"That Brahman is untouched by cause and effect, without interior or exterior. This Atman is Brahman, the experiencer of all things. Such is the instruction of the Vedas." (Brihadaranyaka Upanishd II.v.19)

Passages like these lay emphasis on the Brahman devoid of phenomenal multiplicity. Other passages in the scriptures describe the Causal Brahman [1] and not Brahman as It essentially is. The passages speaking of the primary Brahman are necessarily stronger than those which speak of the secondary Brahman, which is the Causal Brahman. Therefore Brahman should be known as being free from differentiations, and not otherwise, such being the clear evidence of the Vedas. In this way Vyasa establishes the undifferentiated nature of Brahman.

If that be so, the opponent contends, then what will be the fate of the scriptural passages describing Brahman endowed with forms? In reply Vyasa says (Brahma Sutra III.ii.15) that as the luminous sun and moon, when reflected in water and similar substances, appear in diverse forms, so also Brahman, in association with upadhis, assumes various forms. These forms, associated with Brahman, are helpful for worship for beginners. Therefore the instruction about Brahman with form does not conflict with that about the formless Brahman.

[1] Swami Nikhilananda writes, 'Brahman, in association with maya becomes the cause of the universe and is called the Causal Brahman, which is endowed with the attributes of creation, preservation and destruction, and also with those of omniscience, omnipresence, omnipotence, etc. Creation, which is maya, is not an inalienable characteristic of Brahman.'

Sri Sankaracharaya's Introduction to his commentary of Svetasvatara Upanishad translated by Swami Nikhilananda

Answer 2

Swami Vivekananda writes (Complete Works, V3, p 326-7, also available here under the heading Lectures from Colombo to Almora, subheading The Vedanta in All Its Phases - http://cwsv.belurmath.org/volume_3/vol_3_frame.htm):

Now both Shankara and Ramanuja laid aside all claim to originality. Ramanuja expressly tells us he is only following the great commentary of Bodhâyana.

— "Ancient teachers abridged that extensive commentary on the Brahma-sutras which was composed by the Bhagavân Bodhayana; in accordance with their opinion, the words of the Sutra are explained."

That is what Ramanuja says at the beginning of his commentary, the Shri-Bhâshya. He takes it up and makes of it a Samkshepa, and that is what we have today. I myself never had an opportunity of seeing this commentary of Bodhayana. The late Swami Dayânanda Saraswati wanted to reject every other commentary of the Vyâsa-Sutras except that of Bodhayana; and although he never lost an opportunity of having a fling at Ramanuja, he himself could never produce the Bodhayana. I have sought for it all over India, and never yet have been able to see it. But Ramanuja is very plain on the point, and he tells us that he is taking the ideas, and sometimes the very passages out of Bodhayana, and condensing them into the present Ramanuja Bhashya. It seems that Shankaracharya was also doing the same. There are a few places in his Bhashya which mention older commentaries, and when we know that his Guru and his Guru's Guru had been Vedantists of the same school as he, sometimes even more thorough-going, bolder even than Shankara himself on certain points, it seems pretty plain that he also was not preaching anything very original, and that even in his Bhashya he himself had been doing the same work that Ramanuja did with Bodhayana, but from what Bhashya, it cannot be discovered at the present time.