Man is a born philosopher and since the beginning of existence he has been searching for a meaning to life. Key Thinkers in Christianity introduces some of the most brilliant minds we have known and shows the capacity of their ideas to endure the test of time and shape the way philosophy and Christianity have developed throughout history. From Irenaeus in the 2nd century to Hans Urs von Balthasar in the 20th century, this short selection links together some of the most profound ideas of all time, taking the reader on a journey through a history of thought, relevant for both Christian and non-Christian thinkers of the future. Some of the thinkers in this volume were not chosen purely for their insights and observations, but for the fact that other thinkers since have gone back to their ideas, others represent an age or a way of thinking. Although these thinkers are no longer alive, their observations and ideas remain important and their throughts are still the subject of study today. How relevant are the writings of Origen to the aspirations of modern day Christians? To what extent was Athanasius influenced by the thoughts of Origen? What impact did Martin Luther have on Christianity in Northern Europe during the Renaissance? What did Immanuel Kant have to say about Christian thinking? Why has there been a recent resurgence in interest in Kierkegaard's work? Why has there been a recent decline in interest in Bultmann's work? Was Karl Barth the greatest theologian of the 20th century? What did Karl Rahner think of Hans Urs von Balthasar's ideas?