The Christian themes in Marcel’s work are subtle, and often implicit rather than explicit. One of the most fundamental themes is that of the fullness of being. Existence for Marcel is not a void into which we find ourselves thrown, as it seems to be in the writings of many others described as existentialists. It is replete with other people and with an Other that permeates all. This is not an exclusively Christian theme, as Marcel recognizes in his first essay. Nevertheless, it creates an opening to Christianity.
The theme of presence is connected to that of the fullness of being. Presence involves both the subject in the world and the experiences of that subject. It is both being present and receiving the presence of other people and the presence of God through other people and through the world.
Marcel’s writing may seem a bit perplexing to many first-time readers because he does not seem to expound a doctrine or set of ideas in any systematic way. Instead, his writings have the quality of looking around and exploring his thoughts. This can be thought of as a theme in his writing, and a theme that draws on a long tradition in Christian literature. This is the theme of the journey of illumination, in which a writer moves toward understanding through reflection.
Running through all of Marcel’s work is the theme of the mystery, a word with long-standing Christian connotations. The mystery of being is the source of its fullness, and it is the ultimate presence in the world. The distinction between the mystery and the problem parallels the Christian distinction between faith and works. Problems, as issues that have technical and intellectual solutions, involve the works of people. The mystery, though, is something that can be realized only through deepening experience.