Hi Dizzy,
Sacraments bring us God’s grace, ex opere operato, which means that they automatically give us God’s grace, without us having to do anything to deserve it.
The Church did not, from day one say, “There are 7 sacraments and here they are.” What happened is that it received from the apostles certain practices that it discerned as automatically giving grace and that therefore were of divine origin.
The Council of Trent, in its decree on the sacraments, thus summarized the doctrine :
Canon 1.If anyone says that the sacraments of the New Law were not all instituted by our Lord Jesus Christ, or that there are more or less than seven, namely, baptism, confirmation, Eucharist, penance, extreme unction, order and matrimony,[1] or that any one of these seven is not truly and intrinsically a sacrament, let him be anathema.
This does not mean that Jesus sat down one day and said, “Now we are going to talk about the sacraments. Here is the first sacrament : baptism. Tomorrow we’ll talk about confirmation.”
In apostolic days, there was no theology. The apostles did, in some cases, what they had seen Jesus do. In other cases, they did what Jesus told them to do. In other cases they instituted new practices that were based on Jesus’ teachings as they interpreted them with the help of the Holy Spirit.
Verbum