the ministry to which they are called. One would find it incompatible with being in good faith to say that  what defines the faith and practice of the Church is written in stone and has been defined in such a way that no human agency is involved save as an expression of the divine will. 
      Herein lies the problem: all believers have the Holy Spirit dwelling within them. They have the potential to serve in any capacity whatever given their spiritual gifts and whether the church as ordained them formally for service to the laity. One would wish to observe this form for the sake of charity and the good of the institution. Where private worship is concerned no such limitation exists. Lay people can have communion services using wine and a sacramental bread as conscience dictates, for spiritual communion and prayer to honor the Lord and remember Him. One would not call this a Mass per se, nor would one wish to advertise publicly as an ordained minister, or priest.