In Hinduism, self-knowledge is regarded as one of the principal means of knowing God. Among Hindu thinkers, Śaṅkara, the great philosopher and mystic of the Vedānta tradition, emphasizes in his mystical system the distinction between direct and immediate knowledge and empirical and mediated knowledge. He considers true knowledge to be precisely that immediate apprehension which is attained when the self reaches the stage of turīya, or intuitive knowledge that wells up from within. This study, adopting a descriptive-analytical approach, is structured around two fundamental questions: First, from Śaṅkara’s perspective, what is the nature of the states that the self undergoes in order to attain certain knowledge, and how do they differ from one another? Second, what are the characteristics of the turīya stage, and does the self’s progression through these states constitute merely an epistemological process, or does an ontological transformation also occur? The findings of the study indicate that Śaṅkara, by distinguishing between jīva as the individual self and Ātman as the universal self, maintains that in order to attain certain knowledge, the self must pass through three states of consciousness, namely, waking, dreaming, and deep sleep, and reach the stage of turīya, which is the most important stage and the culmination of all the stages. At this stage, the identity of Ātman and Brahman, as the ultimate goal of human knowledge, is revealed. Furthermore, through an analysis of Śaṅkara’s works, it can be argued that this process in fact consists of states of consciousness of the self; however, in light of Śaṅkara’s commentaries on certain Upaniṣads, these states can also be understood in ontological terms.