The title of this collection of essays is Thinking Faith: Moods, Methods, and Mystery, and it might need a word of explanation. The aim is to suggest something of what is involved in thinking faith, while indicating examples of my modest contribution over all these years. Given the exuberant data of faith, beliefs, doctrines and tradition, the task of the theologian is always to reflect on what is so richly given, and to communicate in the most telling fashion its meaning. There are certainly moods that colour the way we think, even though theological writing must show an intellectual concentration of some kind. That is quite compatible with a great variety of approaches, sometimes more hopeful, sometimes more sober, defensive and argumentative. There is also the question of methods. The strange thing about a particular theological method or style of thought is that it is seldom an explicit series of procedures. It is something more spontaneous and formed through the practices of many years. Quite clearly, in this collection of writings a number of methods is implied. Whatever the mood, whatever the method, the mystery remains - of God, Christ, and who we are in that light. To this degree, theology is a way of thinking within mystery, not outside it. In this respect, doing theology is humbling for us theologians when confronted with the limited span of our knowledge - and our poor capacities to express it. There always remain infinite expanses of what is not yet given us to see, so to leave theologians, inarticulate, in splendid defeat. And yet so much has been given, even in the most routine life of the Church, in its Scriptures its sacraments, and in the luminous witness of the many who have gone before us, and live now in the light. Anthony J Kelly, CSsR, is a professor in the Faculty of Theology and Philosophy at Australian Catholic University. A member of the International Theolofical Commission for 10 years (2004-2014), he has written numerous books and articles many of which deal with ecological topics in relation to spirituality and theology. He is at present a Senior Research Fellow in the University's Institute of Critical Inquiry, and is based in Melbourne.