  Unassertability can be read as the key to the apparent paradox of the catuṣkoṭi as well. The venerable text in Majjhima-nikāya 72, relating the teachings of the historical Buddha, offers a precursor for Nāgārjuna's doctrine of the negative tetralemma. Gotama is responding to a monk's question concerning the doctrine of rebirth (quoted in Robinson 1967: 54):