This book is a research monograph which aims to do much more than that. It operates generally within the sphere of comparative religion and is, specifically, a comparative exploration of the role of tradition/Tradition within two distinct faiths, Islam and Christianity. Specific leitmotivs include the roles of authority, fundamentalism, the use of reason, ijtihad> and original comparisons between Islamic Salafism and Christian Lefebvrism. 'Salafism' refers to that strain in Islam which looks backwards to the thought, practices and traditions of the Salaf (pious ancestors); 'Lefebvrism' is a reference to the traditionalist thought and practices of the schismatic Archbishop Marcel Lefebvre (1905—91) who rejected much of the teaching of the Second Vatican Council (1962—65) and what he perceived as that Council's overthrow of tradition/Tradition. It is recognised in my text that the word 'tradition/ Tradition' in both Islam and Christianity has a variety of senses and definitions.