The Upaniṣads, as one of the trilogy of principal Vedāntic texts, the oldest and the most fundamental of them, have exposed a more or less detailed discussion on dreaming, taking it whether as the factual object of their discourse or as a symbol. However, there has been a debate between different schools of Vedāntic philosophy about oneirology, science of dreams and their interpretation, discussion of nature of the dream state, its reality and unreality. This paper, after a short study of oneirology in the Vedas and Upaniṣads, examines argumentations of four great philosophers of different Vedāntic schools, Gauḍapāda, Śaṅkara, Rāmānuja, and Madhva, pertaining to dreams.
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