with Christian missionaries also led to new debates (such as the Panadura debate) and doctrinal works written in defense of Buddhism or attacking Christian ideas, such as Gunapala Dharmasiri's A Buddhist critique of the Christian concept of God (1988). There have also been several modern Theravāda scholars which have taken a historical critical perspective on Theravāda literature and doctrine, attempting to understand its historical development. Some of these figures, such as David Kalupahana, Buddhadasa, and Bhikkhu Sujato, have criticized traditional Theravāda commentators like Buddhaghosa for their doctrinal innovations which differ in significant ways from the early Buddhist texts. The modern era also saw new Buddhist works on topics which pre-modern Buddhists avoided, such as socially engaged Buddhism and Buddhist economics. Thinkers such as Buddhadasa, Sulak Sivaraksa, Prayudh Payutto, Neville Karunatilake and Padmasiri de Silva have written on these topics. Modern scholarship in western languages by western Buddhist monks such as Nyanatiloka, Nyanaponika, Nyanamoli, Bhikkhu Bodhi and Analayo is another recent development in the Theravāda world. Practice (paṭipatti) Textual basis In the Pāli Canon, the path (magga) or way (patipada) of Buddhist practice is described in various ways, one of the most widely used frameworks in Theravāda is the Noble Eightfold Path: The Noble Eightfold Path can also be summarized as the Three Noble Disciplines of sīla (moral conduct or discipline), Samādhi (meditation or concentration) and Paññā (understanding or wisdom). Theravāda orthodoxy takes the seven stages of purification as outlined in the Visuddhimagga as the basic outline of the path to be followed. The Visuddhimagga, a Sinhala Theravāda doctrinal summa written in the fifth century by Buddhaghosa, became the orthodox account of the Theravāda path to liberation in Sri Lanka after the 12th century and this influence spread to other Theravāda nations. It gives the sequence of seven purifications, in three sections: The first section (part 1) explains the rules of discipline, and the method for finding a correct temple to practice, or how to meet a good teacher. The second section (part 2) describes Samatha (calming) practice, object by object (see Kammaṭṭhāna for the list of the forty traditional objects). It mentions different stages of Samādhi. The third section (parts 3–7) is a description of the five khandhas, ayatanas, the Four Noble Truths, dependent origination, and the practise of Vipassanā (insight) through the development of wisdom. It emphasizes different forms of knowledge emerging because of the practice. This part shows