Why can only priests say Mass?

Question: Why can only priests say Mass

Answer:  Catholics believe that the Mass links back, directly, to the Last Supper. At the Last Supper, Jesus instituted the Eucharist and, commissioned the apostles to continue the commemoration of his Passover in the breaking of bread.  The Letters of St Paul and the Acts of the Apostles testify to the key importance of the Eucharist in the life of the early Church. Over time, practices became more ritualised and the person presiding at the breaking of bread was recognised as someone who had received authority through the apostles to preside on behalf of the Church.

Catholics understand this in terms of ordination (whereby the sacrament of Holy Orders is conferred) in a direct apostolic line of succession back to the time of Jesus.  These presiders or ‘elders’ act in the person of Christ. A key point why only priests can celebrate Mass or the Eucharist is that it is more than a mere commemoration: it is a sacramental making present of the sacrifice of Calvary.

Though all Christians share equally in the priesthood of Christ, some have been called to offer the sacrifice of praise and continue the mission of Jesus in administering the sacraments.  Catholics believe that only a validly ordained priest can celebrate Mass and consecrate the bread and wine, which become the Body and Blood of Christ. Now, it is possible that some ‘validly ordained’ priests are illicitly, but validly, ordained.  Such an example occurs when a group of Catholics led by validly bishops act against the instructions of the Pope such as happened recently over the SSPX consecrations of bishops. They are valid but illicit.