[quote="L_Marshall, post:3, topic:343760"]
Altar servers never took vows, in the strictest sense.
What we call an altar server today is a replacement for the Minor Order of Acolyte. There used to be many orders of clergy, including the acolyte, who would serve the Church. Acolytes were men, who often were married and lived within the parish. Eventually, the Order of Acolyte was restricted to those preparing for Major Orders. This made the presence of an acolyte rare in a parish, and led to the use of altar servers as a replacement when an acolyte was not available.
So, to clarify: Acolytes made promises (not vows, only religious make vows), while altar servers have never made vows or promises.
Anyone can make a vow.
It helps to understand that vows may be public or private.
Public vows are recognized by the Church. Someone making public vows is called forth in the name of the Church and undergoes the rite of consecration. God acts through the Church, they are consecrated to (and by) God, and they enter a a new state in life, the consecrated state. Consecration to God through the mediation of the Church is a juridical act - it falls under Church law.
Anyone can make a private vow. A private vow is not a juridical act of the Church. There is no mediation by the Church and the person's state of life is not changed - they do not enter the consecrated state. A private vow is really a continuation, a deepening perhaps, of the person's lay vocation. I have heard it described as an intensification of our baptismal vows.
What confuses people is that private vows can be made in public. One can stand in front of the parish at Mass, in front of a priest, or even in front of a bishop and make a private vow. I know a woman who made a private vow of chastity in front of the congregation at Mass. The Church however does not mediate the private vow and it does not change the person's state.
But anyone can make a private vow. You don't have to be religious to make a private vow. A private vow should be seriously discerned with the help of a spiritual director because you don't just change your mind - you have to be dispensed if you want to get out of it.