Adi Shankaracharya taught:
If the universe be true, let it then be perceived in the state of deep sleep also. As it is not at all perceived, it must be unreal and false, like dreams.
Vivekachudamani 234 (translated by Swami Madhavananda)
On the other hand, the above is refuted by the Brahma Sutras:
(External objects are) not non-existent, for they are perceived. And because of the difference of nature (the waking state is) not (false) like dream etc.
Brahma-Sutra 2.2.28-29 (translated by Swami Gambhirananda)
Non-existence (of things external) is not (true), on account of their being experienced. And owing to the difference of nature (in consciousness between the waking and the dream state, the experience of the waking state) is not like dreams etc.
Brahma-Sutra 2.2.28-29 (translated by Swami Vireshwarananda)
Swami Vireshwarananda commented (in the link above):
The external world is an object of experience through the senses, and cannot therefore be altogether non-existent like the horns of a hare. .... There is a difference between the dream state and the waking state. What is seen in a dream is contradicted by waking experience, it is unreal. The dream state is a kind of memory, but the waking state is a real perception; so it cannot be rejected as untrue. Moreover, what is the proof of the existence of consciousness except experience? If that is so, why should not an object which is experienced be taken also as existing?
Is Advaita refuted by Brahma Sutras?
How does Advaita Vedanta defend itself against the refutation by the Brahma Sutras above?
Is Advaita true and the Brahma Sutras false, or vice versa? How can they both be true?
Swami Vireshwarananda also acknowledged this contradiction in his comments but did not provide further explanation on it:
It may be said that even the Vedantins acknowledge the unreality of the external world, since it is contradicted by the knowledge of Brahman, and that this view is based on the Srutis.
If the Advaitin view is based on the Srutis, then wouldn't that make the Brahma Sutras contradictory to the Srutis?