The connection between the Church and the sacraments is not very clear in the minds of the faithful or even among theologians. The Church dispenses the sacraments, it is said, which are the means of grace for the salvation of the individual. But the relationship between Church and sacraments is often treated almost as if God might have entrusted their administration to some other institution. Karl Rahner sets the question in a wholly new framework by seeing the Church as the enduring presence of Christ in the world and thus as truly the fundamental sacrament, the source of all the sacraments. He emphasizes their importance as signs; they are causes of grace precisely because they are signs and symbols of God's presence. Just as the sacraments are acts fundamentally expressive of the nature of the Church, so the Church experiencing her own nature by fulfilling it, recognises that certain acts flowing from this nature are sacraments. This approach enables the author to show the difference between the opus operatum and the opus operantis not to be as radical as mediocre theology often suggests. He is also able to circumvent the historical difficulty of proving the particular institution by Christ of certain sacraments such as matrimony, holy orders, extreme unction and confirmation. The dispute between Catholics and Protestants over the number of sacraments actually instituted by Christ in Holy Scripture thus becomes a relatively subordinate problem. The book at once provides a new schema for ecumenical discussion, and is bound to provoke much rethinking of traditional Catholic and Protestant statements concerning the sacraments, and will contribute to the deepening of the sacramental lives of many.