In his introduction to Dynamics of Faith, Paul Tillich states: 'There is hardly a word in the religious language, both theological and popular, which is subject to more misunderstandings, distortions, and questionable definitions than the word “faith”' (DF, ix). In his most widely read work, The Courage to Be, Tillich reinterprets the idea of faith, both to correct misconceptions and to enable readers to experience the underlying power and meaning of faith. Because he grounds faith ontologically and existentially, his analysis of faith connects to all functions of human spiritual life and to everyday living. His existential analysis includes psychological aspects of faith and recognizes great diversity in the contents of people's faith, aswell as destructive and sometimes pathological forms of faith. Moreover, Tillich's theological understanding of faith and his critique of forms and contents of faith, while rooted in Christian tradition, extends outside Christianity to include other religions and even secular forms of faith. Discussion of faith for Tillich includes ontological, existential and psychological aspects, with these connecting further to epistemological and ethical dimensions. / Faith as ultimate concern: ontological, existential and psychological dynamics / 'Faith is the state of being ultimately concerned', Tillich asserts in Dynamics of Faith (DF, 1). This formal definition of faith focuses on a person's state of being (ontological), his or her individual connection to ultimacy (ontological, existential and psychological) and the experience of concern (subjective: existential and psychological).