From 1989 until 2007 Kees Waaijman (b. 1942) was 'Professor of the history and systematics of spirituality' at the Radboud University in Nijmegen (NL). During this quarter century his reputation among colleagues world-wide steadily increased. His many publications include the reference book Spirituality: Forms, Foundations, Methods (2000), which has become an international standard work, available in English, German, Italian and Dutch versions (Spanish and Russian versions are forthcoming). Appreciation for Kees Waaijman's contribution to the scientific study of spirituality is expressed in this collection by an international forum of fellow scholars and colleagues in more than forty new explorations of this field. These are arranged in seven sections, containing articles on respectively 'philosophical foundations of spirituality', 'biblical spirituality', 'the history of Christian spirituality', 'Modern Devotion', 'present-day forms of spirituality', 'the relation between spirituality and health care' and 'mysticism and mystagogics'. The authors and editors of this collection trust that these explorations will contribute to the further development of scholarly research into spirituality in years to come.