* Brahman: The ultimate reality, the source and ground of all being. The discussions revolve around understanding Brahman's nature – is it personal or impersonal, conscious or unconscious, etc.? Different Upanishads offer varying perspectives on this.
* Atman: The individual self, the true essence of a person. The central question is the relationship between Atman and Brahman – are they identical (Advaita Vedanta), or distinct yet interconnected? The famous "Tat Tvam Asi" ("That thou art") statement reflects this exploration.
* Karma and Rebirth: The law of cause and effect, and the cycle of birth, death, and rebirth. Understanding karma is crucial for escaping the cycle of samsara (repeated birth and death).
* Yoga and Meditation: Methods for achieving self-realization and union with Brahman. Different paths, including Jnana Yoga (path of knowledge), Bhakti Yoga (path of devotion), and Karma Yoga (path of selfless action) are discussed, although often implicitly through the examples of the individuals involved.
* The nature of consciousness: Understanding the nature of consciousness and its relationship to the body and mind. This is explored through discussions on dreams, deep sleep, and the state of waking consciousness.
* The illusion of the material world (Maya): The Upanishads often portray the material world as an illusion or temporary manifestation of Brahman. Understanding this illusion is essential for liberation.
* The meaning of life and death: The ultimate goal of human life as depicted in the Upanishads is the realization of one's true nature (Atman) and its unity with Brahman. Death is viewed not as an end but as a transition in the cycle of rebirth.
It's important to note that the "students" and "teachers" in the Upanishads are not learning and teaching in a structured curriculum. The discussions are often philosophical debates and spiritual inquiries, aimed at profound understanding and self-realization rather than acquiring specific factual knowledge.