Freedom and sin. Man's freedom is limited and fallible. In fact, man failed. He freely sinned. By refusing God's plan of love, he deceived himself and became a slave to sin. This first alienation engendered a multitude of others. From its outset, human history attests the wretchedness and oppression born of the human heart in consequence of the abuse of freedom.
Source: Catechism of the Catholic Church (Vatican.va)