The focus (tatparyam) of Mandukya Upanisad is only on the fourth quarter (Turiya). In this 7th mantra, Turiya is revealed as the non-dual substratum by mere negation (apavada) of the first three quarters, Visva (waker), Taijasa (dreamer) and Prajna (sleeper, causal state).
Please note –
A certain preparedness is required for self-knowledge. Before listening to the teachings of the upanisads, we suggest you begin with listening to an ‘Introduction to Vedanta’ and ‘Tattvabodha’ audio series – both of which will give the novice listener a greater insight into the Vision of Vedanta and the importance of following the traditional methodology of teaching.