In theology, an article of faith or doctrine which defies man's ability to grasp it fully, something that transcends reason, is called "a mystery of the faith". The Catechism of the Catholic Church speaks of the Trinity as "a mystery of faith in the strict sense, one of the 'mysteries that are hidden in God, which can never be known unless they are revealed by God'", and it declares: "The mystery of the Most Holy Trinity is the central mystery of Christian faith and life. It is the mystery of God in himself. It is therefore the source of all the other mysteries of faith, the light that enlightens them." The Church itself is "a mystery of the faith".