Marriage is a permanent partnership of love and life between a man and a woman in which ‘the two become one flesh.” God established marriage as the way of giving and receiving love and continuing the human race.
The requirement that a priest (or other official Catholic witness, normally a deacon) witness a marriage is necessary only for marriages involving at least one Catholic. In all marriages, sacrament or not, the woman and man exchange consent and so enter into marriage. In marriages involving Catholics, the law of the Church obliges the woman and man to exchange their consent before two witnesses and an official Catholic witness (normally a priest or deacon) in order for that marriage to be valid.
The Catholic Church believes that every valid, sacramental and consummated marriage is indissoluble. This is our understanding of God’s law as found in the Scriptures, as well as 2,000 years of Catholic teaching.