A Sacrament is “a rite in which God is uniquely active.” Jesus never used the term sacrament nor any of the New Testament authors ever mentioned the term sacrament. In the New Testament we hear about baptism and the breaking of the bread. But these two Christian rituals were not called sacraments. Even in the early documents such as Didache, Letters of Ignatius of Antioch, the Apology of Justin, the Apostolic Tradition of Hippolytus we do hear about baptism and Eucharist but no general term as sacrament. While in the east they used the term Mystery to designate the sacraments, in the West, Tertullian was the first person who use the term Sacramentum. He used the term for many elements of Christian faith like the trinity; the saving act of God. In baptism and Eucharist Tertullian saw the mysterious presence of God. Hence his use has nothing to do with an elaborate sacramental theology.
It is only with St. Augustine that we find a real sacramental theology and for him there were only two sacraments namely baptism and Eucharist. He defines a sacrament: “a sacred sign or visible word”. For him, there is a hidden, mysterious reality which enters into our human world through special signs. Concerning the Eucharist he says “….How is the bread His Body? And the cup, or what is in the cup, how is that blood? These things, my brothers, are called sacraments for the reason that in them one thing is seen, but another is understood. That which is seen has physical appearance that which is understood has spiritual fruit” (Sermon 272). The distinction between the reality and sign is the basis of his sacramental theology. (OSBONE K B., Sacramental Theology, pp. 20 ff)
Why did the Fathers of the Church call baptism and Eucharist sacraments? These two Christian rituals reveal the salvific design of God, the Eucharist right from the beginning was the celebration of the remembrance of the Lord, his passion, death and resurrection. We have seen that the early Christians never felt the absence of Jesus in this celebration. It was the Lord who spoke; it was he who nourished them. Also they were influenced by the Hellenistic rites of mystery.
St. Thomas Aquinas continued and made perfect the speculation started by Augustine regarding the sacraments, he held the view that all the sacraments were instituted by Christ himself. It was the view of St. Thomas that the sacraments are the instrumental cause of God’s grace (Tour of Summa, 363-389). After the glorious period of scholasticism, there was a considerable decline and the subsequent rejection of some of the sacraments by the reformers, the Council of Trent repeated the necessity of sacraments for salvation.