Gabriel Marcel has been described as a theistic or Christian existentialist. Born in Paris of Protestant parents, he converted to Roman Catholicism in 1924. Prior to his conversion, he had immersed himself in idealism, as his first book, a study of Royce's metaphysics, reveals. Before Jaspers and Heidegger were known to French intellectuals, Marcel had written about themes central to existentialism, but with a religious twist. He had acknowledged concern for the vitality and pervasiveness of religious experience, and, like Martin Buber, he had pointed to the sociality of human experience, which bears witness to the presence of the Divine. For Marcel, Being involves participation. No one can be separated from the whole of Being to which he or she is related. Nor can a person be reduced to merely a facet of Being; for he or she is a concrete individual, with experience that is immediate, spontaneous, unpredictable. Though entranced by the mystery of existence, a person may illuminate it by means of philosophical reflection.