Tim Keller, in an excellent article called Evangelistic Worship, has a section headed ‘Three Practical Tasks,’ which begins with No. 2, ‘Getting Unbelievers into Worship’.

The numbering is not a mistake. This task actually comes second, but nearly everyone thinks it comes first! It is natural to believe that non-Christians must get into worship before “doxological evangelism” can begin. But the reverse is the case. Non-Christians do not get invited into worship unless the worship is already evangelistic. The only way to have non-Christians in attendance is through personal invitation by Christians. Just as in the Psalms, the “nations” must be directly asked to come. But the main stimulus to building bridges and issuing invitations is the comprehensibility and quality of the worship experience.

Christians will instantly sense if a worship experience will be attractive to their non-Christian friends. They may find a particular service wonderfully edifying for them and yet know that their nonbelieving neighbors would react negatively. Therefore, a vicious circle persists. Pastors see only Christians present, so they lack incentive  to  make  their  worship  comprehensible  to  outsiders.  But  since  they  fail  to  make  the  adaptations, Christians who are there (though perhaps edified themselves) do not think to bring their skeptical and non-Christian friends to church. They do not think they will be impressed. So no outsiders come. And so the pastors respond only to the Christian audience. And so on and on. Therefore, the best way to get Christians to bring non-Christians is to worship as if there were dozens and hundreds of skeptical onlookers. And if you worship as if , eventually they will be there in reality.

The article is full of great ideas for making Sunday morning services genuinely evangelistic, and they can be applied as easily to liturgical services as to any others. Do read the whole thing. It’s here.