It has become a practice to see the contents of the Upanishads purely from an intellectual viewpoint. According to the seers of the Upanishads, the truths in these books should be realised by every individual.
The process of realisation is termed "Sadhana". The Upanishads are manuals of Sadhana. The hints for Sadhana are called "vidyas". Lights on the Upanishads contains a detailed discussion of six vidyas.
Within the purview of the six vidyas discussed here, the author has hinted at several modes of consolidation of Sadhana. It will help the Sadhaka "to evolve himself to the stature whose range spreads from mere materiality" to the divine levels of consciousness.