- Adi Shankara says that whatever thing remains eternal is true, and whatever is non-eternal is untrue. Since the world is created and destroyed, it is not true.
- Truth is the thing which is unchanging. Since the world is changing, it is not true.
- Whatever is independent of space and time is true, and whatever has space and time in itself is untrue.
- Just as one sees dreams in sleep, he sees a kind of super-dream when he is waking. The world is compared to this conscious dream.
- The world is believed to be a superimposition of the Brahman. Superimposition cannot be true.
On the other hand, Adi Shankara claims that the world is not absolutely false. It appears false only when compared to Brahman. In the pragmatic state, the world is completely true—which occurs as long as we are under the influence of Maya. The world cannot be both true and false at the same time; hence Adi Shankara has classified the world as indescribable.
Full article: Status of the world according to Advaita Vedanta