The Mūlamadhyamakakārikā (Sanskrit) or Fundamental Verses on the Middle Way, is a key text of the Madhyamaka-school, written by Nagarjuna.
The Mūlamadhyamakakārikā is Nagarjuna's best known work. According to Kalupahanna, it is
[N]ot only a grand commentary on the Buddha's discourse to Kaccayana, the only discourse cited by name, but also a detailed and careful analysis of most of the important discourses included in the Nikayas and the agamas, especially those of the Atthakavagga of the Sutta-nipata.
According to Kalupahanna, in this work,
Utilizing the Buddha's theory of "dependent arising"(pratitya-samutpada), Nagarjuna demonstrated the futility of [...] metaphysical speculations. His method of dealing with such metaphysics is referred to as "middle way" (madhyama pratipad). It is the middle way that avoided the substantialism of the Sarvastivadins as well as the nominalism of the Sautrantikas.
According to Kalupahanna, Nagarjuna insisted that...
[A]ll experienced phenomena are empty (sunya). This did not mean that they are not experienced and, therefore, non-existent; only that they are devoid of a permanent and eternal substance (svabhava). Since they are experienced, they are not mere names (prajnapti).
Because of the high degree of similarity between the Mūlamadhyamakakārikā and Pyrrhonism, particularly the surviving works of Sextus EmpiricusThomas McEvilley suspects that Nagarjuna was influenced by Greek Pyrrhonist texts imported into India. However, since Pyrrho of Elis is known to have visited India, it is also suspected that his formulation of the Three Marks of Existence and the tetralemma was influenced by Buddhist and Jain philosophers (the so-called gymnosophists) from whom he is known to have learnt during his travels to India.