Nāgārjuna was an Indian Buddhist thinker central to the Mādhyamaka school of Mahāyāna Buddhism. He lived from approximately 150 to 250 and continued the classic Buddhist approach to liberation from suffering through mental discipline.
Nāgārjuna’s innovation was the concept of “emptiness,” or śūnyatā. This is a recognition that things have no meaning in themselves; instead, they derive significance from their relationship to other things. (For example, “day” has no meaning apart from “night.”) This contextual understanding of meaning is called pratītya-samutpāda, or “dependent co-arising.”
Despite the essential emptiness of the categories that people employ to understand the world, on a pragmatic level people have to use those categories in order to live. In terms of ethics, Nāgārjuna’s contribution was to separate ultimate from conventional truths, so that although people should live fully aware of the basic illusoriness of reality, they should also uphold a moral path in their daily lives. Rather than release from this world (nirvāna), Nāgārjuna believed the ideal to be that of the bodhisattva, or “enlightened being”: living in the world but being aware of its insubstantiality, and working for the benefit of all beings.
Nāgārjuna’s thought has influenced Buddhism in Tibet, China, Korea, and Japan for the nearly two millennia since his death, particularly in the Zen tradition.