I guess it has become very obvious in all my previous letters that I am much closer to ancient Asian philosophies than to European philosophical traditions. I find the classical Indian and Chinese exegeses on holistic and non-separative ontology, constructivist and naturalistic epistemology, and especially the pragmatic and psychologistic (in contrast to many Western meta-ethicists, for me that is something positive) ethics conceptualisations much more plausible and convincing than the premature and naïve Western realism, dualism, substance metaphysics and transcendentalism. The most famous figures in ancient Asian philosophy are certainly Siddhartha Gautama (the historical Buddha), Laozi (even though it is not certain that this was one real person) and Kongzi (Confucius). They are regarded as the founders of Buddhism, Daoism, and Confucianism, respectively. However, in each schools of thought, there are other thinkers that achieved much greater insights than their predecessors: Zhuangzi put the Daoist philosophy on more solid grounds, Mengzi (Mencius) and Xunzi sophisticated Kongzi’s ideas substantially, and Nagarjuna is without any doubt the most important and influential Buddhist philosopher before it became a modern academic discipline! His enormous merits in advancing the insights on Sunyata (emptiness), Satyadvaya (Two Truths), Madhyamāpratipad (the Middle Way) and Pratītyasamutpāda (Dependent Origination) make him my personal hero in the category Ancient Philosophy!
Nagarjuna (Sanskrit: नागार्जुन, Chinese: 龍樹) lived in South India around 150-250CE (widely shared scholarly view). According to the legend, he received the Prajñāpāramitā sutras from mystical creatures called “Naga” (a mix of snake and dragon) who kept in on behalf of the historical Buddha at the bottom of a lake. His name means “white snake”, and he is often depicted with snakes (an Indian symbol for wisdom) around his head. The historical record of his works is incomplete and still vividly debated among contemporary scholars. Some of the text attributed to him might be from other philosophers. It is widely acknowledged that his major contribution is the Mūlamādhyamakakārikā, a treatise of 27 chapters on The Middle Way.
After the death of Siddhartha Gautama, his followers split, basically, into two groups: The worshippers who focused on the practices taught by Buddha, and the scholars who wanted the Dharma (transferred in the sutras of the Pali canon) to be understood as philosophical wisdom. The former can be regarded as the religious interpretation of Buddhism, the latter as the philosophical school. For around 400 years, it seemed that the worshippers were the predominant group. The theoretical schools divided further and further and disputed with one another about who represents the true Dharma and who understands Buddha’s teachings in the best and most appropriate way. By the time of Nagarjuna, the original philosophy conveyed in Buddha’s doctrines were at the risk of being lost. Nagarjuna’s analysis of the concepts mentioned above formed a new firm connection between our philosophical understanding with Buddha’s original accounts. He is regarded as the founder of the Madhyamaka school in the Mahayana branch of Buddhism.
As pointed out earlier, I regard the 12 links of interdependent co-arising as the core of Buddhist teachings, even more fundamental than the Four Noble Truths or the Eight-fold Path (which are rather easy-to-understand doctrines of folk Buddhism, in my humble opinion). Once familiar with this model, it is easy to understand the difficult notions of sunyata (emptiness) and the practical implications of a Middle Way philosophy (which is the center of Nagarjuna’s teachings). Thanks to Nagarjuna we have today a better and philosophically more grounded idea of these important elements of Buddhist worldview. I can see how it applies to many daily life situations and how I can make use of it to increase my life quality. For a philosophical Buddhist (but probably also for religious ones), Nagarjuna’s writings are essential reads, but there is also a lot of good and insightful secondary literature about him and his teachings (see a list in this article by Jan Westerhoff in the Standford Encyclopedia of Philosophy). If you want to gain deeper insights into Buddhist thinking, there is no way around Nagarjuna, but it is definitely a way that is worth the time and effort!