In The Christian Faith, Henri de Lubac makes this comment regarding the Patristic view of conversion:
“Becoming a Christian did not mean merely giving up erroneous beliefs in order to embrace the true teaching offered by the Church; it meant, essentially, renouncing Satan in order to adhere to Christ, or, as St. Justin put it, turning from idols in order to consecrate oneself through Christ to the unbegotten God. It meant, as Hermas said in his vivid language, apostatizing from the angel of evil in order to follow the angel of justice and to live for God.” (pp. 143-144).
de Lubac goes on to show that to the early Fathers, faith was a whole-person commitment to follow Jesus and live, by the power of the Holy Spirit, to the glory of God. Faith of course involves believing that which has been revealed, but it is more than this. Faith means entrusting oneself to God; pledging the whole being to the Savior who has given Himself to us first. Thus, de Lubac notes, faith “calls to mind the reciprocal gift of spouses.” The bridegroom offers himself and all that he is to the bride promising never to leave or forsake her and the bride responds by giving herself to him without reservation “til death do us part.”
In the old wedding vows there was the phrase, “I pledge thee my troth.” Troth is the old English word for fidelity, loyalty, faithfulness. Marriage involves a happy resignation of the former “single” life in exchange for the new life in union with another. This “betrothing” involves “dying” to the old way of life (living by yourself), in order to be “resurrected” to the new life of marriage. It is a very real “conversion” for both parties. And every marriage exists and prospers only so long as both parties maintain their troth. If troth is lost and forsaken permenantly, the marriage will die.
In the same way, faith in Jesus inescapably involves a commitment to loyalty which is manifested in day by day faithfulness. It involves a willing breaking with the old life of living for self and following other gods, in order to enter the new life of love, submission, and communion with the One living and true God who has revealed Himself in His Son. Living by faith means persevering in resisting the devil, refusing to be conformed to the world of unbelief, and making no provision for the flesh. When this loyalty and willing fidelity is lost, faith has died.
To emphasize this aspect of faith is not to deny the role of knowledge or assent in believing, but it clearly distinguishes the faith of the Church from all other belief. Without this element of commitment, there is no faith. The devils may “believe and tremble” but they do not entrust themselves to God. They never “pledge their troth.” Though they may believe, they do not have faith.