In the course of a recent conversation on this topic, I brought up the example of the mysterious character that attaches to the presence near one of a sleeping person, especially of a sleeping child. From the point of view of physical activity, or at least in so far as the notion of physical activity is defined in relation to the possible grasping of things, the sleeping child is completely unprotected and appears to be utterly in our power; from that point of view, it is permissible for us to do what we like with the child. But from the point of view of mystery, we might say that it is just because this being is completely unprotected, that it is utterly at our mercy, that it is also invulnerable or sacred. And there can be no doubt at all that the strongest and most irrefutable mark of sheer barbarism that we could imagine would consist in the refusal to recognize this mysterious invulnerability. This sacredness of the unprotected lies also at the roots of what we might call a metaphysics of hospitality.
Gabriel Marcel, The Mystery of Being, Part I, Chapter X.