82 Today, cooperation includes new forms-not only economic assistance, but also direct participation. New situations connected with the phenomenon of mobility demand from Christians an authentic missionary spirit. International tourism has now become a mass phenomenon. This is a positive development if tourists maintain an attitude of respect and a desire for mutual cultural enrichment, avoiding ostentation and waste, and seeking contact with other people. But Christians are expected above all to be aware of their obligation to bear witness always to their faith and love of Christ. Firsthand knowledge of the missionary life and of new Christian communities also can be an enriching experience and can strengthen one's faith. Visiting the missions is commendable, especially on the part of young people who go there to serve and to gain an intense experience of the Christian life. Reasons of work nowadays bring many Christians from young communities to areas where Christianity is unknown and at times prohibited or persecuted. The same is true of members of the faithful from traditionally Christian countries who work for a time in non-Christian countries. These circumstances are certainly an opportunity to live the faith and to bear witness to it. In the early centuries, Christianity spread because Christians, traveling to or settling in regions where Christ had not yet been proclaimed, bore courageous witness to their faith and founded the first communities there. More numerous are the citizens of mission countries and followers of non-Christian religions who settle in other nations for reasons of study or work, or are forced to do so because of the political or economic situations in their native lands. The presence of these brothers and sisters in traditionally Christian countries is a challenge for the ecclesial communities, and a stimulus to hospitality, dialogue, service, sharing, witness and direct proclamation. In Christian countries, communities and cultural groups are also forming which call for the mission ad gentes , and the local churches, with the help of personnel from the immigrants' own countries and of returning missionaries, should respond generously to these situations. Missionary cooperation can also involve leaders in politics, economics, culture and journalism, as well as experts of the various international bodies. In the modern world it is becoming increasingly difficult to determine geographical or cultural boundaries. There is an increasing interdependence between peoples, and this constitutes a stimulus for Christian witness and evangelization.
Source: Redemptoris Missio (Vatican.va)