In his second encylical, Spe Salvi, Pope Benedict XVI explains that faith ought to be for us “performative” rather than merely “informative.” He writes:
Christianity was not only “good news”—the communication of a hitherto unknown content. In our language we would say: the Christian message was not only “informative” but “performative”. That means: the Gospel is not merely a communication of things that can be known—it is one that makes things happen and is life-changing. The dark door of time, of the future, has been thrown open. The one who has hope lives differently; the one who hopes has been granted the gift of a new life. 
We do not often take the time to ponder and to recognize the infinite implications of professing our faith in the God of Jesus Christ. As MJ Andrew recently made clear in his post on the authority of Catholic Social Doctrine, as we convert or revert to Catholicism all of our priorities, our preconceived notions, our positions, and our perceptions should be re-ordered according to the Faith.
However, for many this second conversion never happens. Cradle Catholics are unintentionally taught to view their “religion” – faith in the God who became man to suffer and die for us so that we may become like Him – as merely another subject in school, a blow-off elective at that. As a result we see an ever growing cafeteria Catholicism. I believe the term could apply to many more of us than we are comfortable admitting. Though they(we?) profess to being members of the Body of Christ, many Catholics are more Republican, Democrat, American, Marine, Sorority, Fraternity, fan, etc. than Catholic. They may not explicitly or consciously reject any doctrines of the faith, but their lives fail to reflect their alleged discipleship. They live just like other members of society, sharing the same vices and virtues. This is simply not acceptable and is the reason why the secular world has no difficulty rejecting the claims of the Gospel.
In his book Introduction to Christianity, Joseph Ratzinger explains why this faith as knowledge is insufficient for effecting radical change in our lives.
Calculable practical knowledge is limited by its very nature to the apparent, to what functions, and does not represent that in which to find truth itself, which by its very method it has renounced. The tool with which man is equipped to deal with the truth of being is not knowledge but understanding: understanding of the meaning to which he has entrusted himself. And we must certainly add that “understanding” only reveals itself in “Standing”, not apart from it. One cannot occur without the other, for understanding means seizing and grasping as meaning the meaning that man has received as ground. I think this is the precise significance of what we mean by understanding: that we learn to grasp the ground on which we have taken our stand as meaning and truth; that we learn to perceive that ground represents meaning. 
In light of this we should be examining our own lives, asking ourselves how firm is my assent of the heart? Do I stand on the ground which is the Logos or do I merely know of it as a datum? If I do stand on that ground which is the Rock, the cornerstone which the world has rejected, the way I see the entire world, the meaning I give to it, shall be changed.
So now we must ask explicitly: is the Christian faith also for us today a life-changing and life-sustaining hope? Is it “performative” for us—is it a message which shapes our life in a new way, or is it just “information” which, in the meantime, we have set aside and which now seems to us to have been superseded by more recent information? 
Our reason must continue to seek, to take up that to which our hearts have assented while our will continually confirms and strengthens that assent. Ratzinger explains how this assent manifested itself in integral Christian witness in the lives of the earliest Christians.
Christians rejected even the most harmless forms of cult, such as putting one’s name down on the list of those contributing to the cost of a sacrificial victim, and were ready to risk their lives by such an action. Today, in a case like this, one would distinguish between the unavoidable act of civic loyalty and the real religious act, in order to find an acceptable way out and at the same time to take account of the fact that heroism cannot be expected of the average man. Perhaps such as distinction is today really possible in certain circumstances as a result of the decision carried out at the time. In any case it is important to realize that this refusal was far from being a piece of narrow-minded fanaticism and that it changed the world in a way in which it can only be changed by the readiness to suffer. Those events showed that faith is not a matter of playing with ideas by a very serious business: it says no, and must say no, to the absoluteness of political power and to the worship of the might of the mighty in general –“He has put down the mighty from their thrones” (Lk 1:52); and in doing so it has shattered the political principle’s claim to totality once and for all.
What harmless activities, associations, beliefs, and perceptions need we reject as being unChristian? Do I eat as one who is aware of the members of the Body who starve? Do my economic intuitions reflect solidarity, subsidiarity, and the preferential option for the poor? Do my attitudes towards strangers, enemies, and the other reflect those of the Good Samaritan? Do I place my hope in my power, money, affluence or in the poverty of Christ’s omnipotent Love?
May God give us the grace and gratuitousness to respond to his Gift of Self by abandoning ourselves to Him and allowing ourselves to be transformed by the God who is love.
 Pope Benedict XVI, Spe Salvi, 2  Joseph Ratzinger, Introduction to Christianity, (San Francisco, Ignatius Press), 77.  Spe Salvi, 10.  Intro to Christianity, 112-113.