The paper deals with the life and work of an outstanding Christian French philosop_her of the XXth century Jean Guitton (1901-1999). First, the author exa_mines Guittonś relationships with the important Christian thinkers of the XXth century, in particular with M. Blondel and Pierre Teilhard de Chardin. He focuses on three of Guittonś works, namely Temporal existence (1948), Purgatory: A Deep Mystery (1957) and Silence about the Essential (1948). In the first of these three books he points out to the originality of Guittonś understanding of time, which enabled him, drawing from Blondel, to develop further the ontology of activity in the evolutionary dynamics of being. Next, he sheds light on Guittonś new understanding of purgatory in his second of the above mentioned works, inspired mainly by the visions of St. Catharine of Genoa. In his third work he focuses on a topical problem of tolerance and truth in the context of the internal Christian dialogue.