Robert Jenson on sacraments

The Western catholic tradition has insisted above all on two propositions about sacraments. First, sacraments are signs; they mean something, and that something is the gospel. This proposition has been established above all by the dicta of Augustine. Second, sacraments are events of grace; they accomplish something, and that something is the new reality of which the gospel speaks.

From Christian Dogmatics, Vol. II, (Fortress, 1984), 305.