In 1971, the International Synod in Rome published "Justitia in mundo".  It states "action on behalf of justice and participation in he transformation of the world fully appear to us as a constitutive dimension of the preaching of the Gospel.  For the first time, the church stated that IT had a need to bear witness to justice in its own life if its call for justice in he world is to be credible. 
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David J. O'Brien and Thomas J. Shannon, eds., CATHOLIC SOCIAL THOUGHT: THE DOCUMENTARY HERITAGE [Maryknoll, N.Y.: Orbis, 1992) p. 289.