The Dvaita or dualist school of Vedanta philosophy in Hindu religion originated in the 13th-century in South India with Sri Madhvacharya (Madhva). How can unreal appear? – This question is answered by the following probe in Madhwa School of philosophy.
Do they, who refute the appearance of the unreal, have the cognition of the unreal or do they not? If they have refutation is not possible. If they do not have, even then the refutation is not possible. Those who say that silver which appears on a conch shell is asat cannot do so without congnizing asat.
Madhvacharya has made a unique observation on the occurrence of error. Two real objects are necessary for the occurrence of any error: one in the form of substratum or base of superimposition and the other as a real of the superimposed.
Therefore the illusoriness of the world is a sheer impossibility.
Source - Notes taken from Encyclopedia of Hinduism Volume III - page 560 - IHRF - Rupa - 2011