Sravan is sufficient
In Sravan, the student listens to the teacher about the teaching, namely, TTA. On understanding the full import of TTA, the student has Self-knowledge, i.e., I am Brahman and there is liberation. Self-knowledge and liberation are simultaneous. There is no time-gap. In chapter 18 titled ‘Tat Tvam Asi’ of Upedesha Sahasri (Up Sah), ShankarAchArya introduces a Purva Paksha (PP) in 18.09 who holds that mere Sravan is not sufficient for liberation. It should be followed by repetition of ‘I am Brahman’. PP argues as below.