My apologies to anybody who saw the draft that was published the other day, but its been a hectic time for us writers getting back to uni and restarting lectures, resulting in it being left as a draft for ages and accidentally getting published, by somebody else, without a proper look at what they posted.
A priest must be easily distinguishable from the people to whom he has been sent, for by his ordination he has been set apart for a special task. He has been sent to serve the people of God first and foremost in the sacraments, secondly by teaching them the decrees of God, yet still doing all of this in a pastoral, charitable manner. He must be easily distinguished that he may easily be called from what he is doing to help.
If a priest then is to wear civvies (so to speak), or even to simply remove the collar from his clerical shirt, he is denying his priesthood, he is denying what God has done for him and by him. He is denying his position to serve all people’s by his priesthood. But by wearing his cassock he is making it obvious to all around I am a priest, I am here to serve God through His people. Even still in his clerical shirt and trousers a priest will look like a businessman from a distance or from behind. If a priest is to go around wearing his cassock he is making a clear statement ‘I am here to serve God in his people.’ The cassock then is a mark of servitude.
As a mark of servitude the anybody who serves on the sanctuary should be wearing a cassock. Not only does it looks better if Altar servers wear the cassock and cottar rather than an alb, but it’s also a reminder for them and all around they are here to serve the priest, still being clearly differentiated from the priest, while he as functioning as Christ (see my post on persona Christi). For your servers to be primarily those upon whom the minor order of acolyte (a preparation for Holy Orders whilst in the later years of seminary ) has been conferred, or even just seminarians is a great symbol of continuity within the Church, it is to say you can prepare for your Holy Orders and priesthood by being given the task of serving the Mass and the cassock comes with it. To see this happening is a witness to the continuity of the Church, this however is simply not possible in many places at the moment as we just font have the seminarians (yet).
As the priest first and foremost is serving Christ in the people he has been sent to serve he should wear his cassock to the Mass, and over this is the sacred vestments as stated by the GIRM (General Instruction of the Roman Missal). This gives the instruction that “the sacred vestments should also contribute to the beauty of the sacred action itself. It is appropriate that the vestments to be worn by priests and deacons, as well as those garments to be worn by lay ministers, be blessed according to the rite described in the Roman Ritual before they are put into liturgical use.” section 335. This reminds us that nobody can wear just anything to Mass and even less so if we are to assist in the liturgy in any way, the laity too must be come dressed in their Sunday best before coming on the altar according to the missal, but that carries to everybody else.