Above all the vision of Frank Duff concerning the priest and laity can only be understood in the context of evangelisation and the salvation of souls. Both priest and laity must be totally christocentric and the central focus of Christ is the salvation of souls.
Our Lord put it categorically more than once: 'I came to save sinners.' Evangelisation is simply cooperating in the work of redemption. It is facilitating a meeting between Christ and another person, bringing the fruits of redemption to others or again putting it very simply, it is helping others get into heaven.
This must be the overwhelming focus of any priest or layperson who would wish to be apostolic. Ultimately there is no evangelisation without focusing on the salvation of souls. Whatever the immediate goals, the ultimate goal of all evangelisation must be the gaining of eternal life.
The Code of Canon Law puts it very succinctly: For all activity of the Church 'the salvation of souls must always be the supreme law. '(Can.1752) This is the identity of interest between the priest and the lay apostle.