Acharya Prashant explains the concepts of Vidya and Avidya as discussed in the Ish Upanishad. He describes how the human mind tends to divide existence into the self and the universe, creating a false distinction between the internal and external. This separation is represented by Vidya (knowledge of the self) and Avidya (knowledge of the universe). He argues that true understanding arises only when one sees these two together as mirror images of each other. By knowing the subject and the object simultaneously, one reaches a state of witnessing that is separate from duality.