Francis Shaeffer on evidence

The world has a right to judge whether we are Christians or not by the way we show an observable love to all true Christians, and therefore our love for each other as true Christians must be evident to the world. Furthermore, Christ tells us in John 17 that the world has a right to judge whether the Father has sent the Son on the basis of whether the world sees love among all true Christians.

~ Francis Shaeffer,

The New Super-Spirituality (1972), p. 24