261 Venerable Brethren and dear sons, We began with that wonderful Encyclical of Pope Leo, and passed in review before you the various problems of our modern social life. We have given principles and directives which We exhort you earnestly to think over, and now, for your part, to put into effect. Your courageous co-operation in this respect will surely help to bring about the realization of Christ's Kingdom in this world, "a kingdom of truth and life; a kingdom of holiness and grace; a kingdom of justice, of love and of peace," (63) which assures the enjoyment of those heavenly blessings for which we were created and for which we long most ardently.
Source: Mater et Magistra (Vatican.va)