The main teaching of Ramesh Balsekar, a renowned Advaita teacher, is the concept of non-duality or Advaita, which is rooted in the ancient Indian philosophy of Vedanta. Balsekar's teachings revolve around the idea that there is only one ultimate reality, and everything else is an illusion or a manifestation of that reality.

Balsekar emphasizes that the true nature of this reality, also known as Brahman, is beyond human understanding and cannot be described or conceptualized. He believes that the mind, with its limited capacity, is unable to grasp the true essence of reality and can only perceive it through the filter of its own conditioning and beliefs.

According to Balsekar, the root cause of all suffering and dissatisfaction in life is the mistaken identification with the individual self or ego. He asserts that the ego is an illusion created by the mind and is not the true self. The true self, or the Atman, is the unchanging, eternal, and pure consciousness that exists within every being.

Balsekar's teachings also emphasize the concept of surrender or acceptance of what is, without any resistance or attachment. He encourages individuals to let go of their desires and expectations and instead trust in the flow of life and the unfolding of events as they are meant to be.

In his teachings, Balsekar also emphasizes the importance of self-inquiry and introspection to understand one's true nature and break free from the illusions created by the mind. He encourages individuals to question their beliefs, thoughts, and perceptions to uncover the truth that lies beyond them.

Balsekar's teachings are not limited to theoretical concepts but also emphasize the practical application of these principles in daily life. He encourages individuals to live in the present moment and to let go of worries about the past or future. He also emphasizes the importance of living a life of simplicity, humility, and compassion.

In conclusion, the main teaching of Ramesh Balsekar is the concept of non-duality or Advaita, which emphasizes the oneness of all existence and the illusion of the individual self. His teachings revolve around the idea of surrender, self-inquiry, and living in the present moment to break free from the illusions of the mind and experience the true essence of reality.