From Pope Paul VI’s Evangelii Nuntiandi (On Evangelization in the Modern World)

Above all the Gospel must be proclaimed by witness. Take a Christian or a handful of Christians who, in the midst of their own community, show their capacity for understanding and acceptance, their sharing of life and destiny with other people, their solidarity with the efforts of all for whatever is noble and good. Let us suppose that, in addition, they radiate in an altogether simple and unaffected way their faith in values that go beyond current values, and their hope in something that is not seen and that one would not dare to imagine. Through this wordless witness these Christians stir up irresistible questions in the hearts of those who see how they live: Why are they like this? Why do they live in this way? What or who is it that inspires them? Why are they in our midst? Such a witness is already a silent proclamation of the Good News and a very powerful and effective one. Here we have an initial act of evangelization. The above questions will ask, whether they are people to whom Christ has never been proclaimed, or baptized people who do not practice, or people who live as nominal Christians but according to principles that are in no way Christian, or people who are seeking, and not without suffering, something or someone whom they sense but cannot name. Other questions will arise, deeper and more demanding ones, questions evoked by this witness which involves presence, sharing, solidarity, and which is an essential element, and generally the first one, in evangelization.