(CG 4/58). Of the Number of the Sacraments of the New Law (Book 4. God, in His Revelation) (Summa Contra Gentiles) (Aquinas, Thomas, St.)

THE generation of a living thing is a change from not living to life. Now a man is deprived of spiritual life by original sin; and whatever sins are added thereto go still further to withdraw him from life. Baptism therefore, or spiritual generation, was needed to serve the purpose of taking away original sin and all actual sins. And because the sensible sign of a Sacrament must be suited to represent the spiritual effect of the Sacrament, and the washing away of filth is done by water, therefore Baptism is fittingly conferred in water sanctified by the word of God. And because what is brought into being by generation loses its previous form and the properties consequent upon that form, therefore Baptism, as being a spiritual generation, not only takes away sins, but also all the liabilities contracted by sins,�all guilt and all debt of punishment: therefore no satisfaction for sins is enjoined on the baptised.

With the acquisition of a new form there goes also the acquisition of the activity consequent upon that form; and therefore the baptised become immediately capable of spiritual actions, such as the reception of the other Sacraments. Also there is due to them a position suited to the spiritual life: that position is everlasting happiness: and therefore the baptised, if they die fresh from baptism, are immediately caught up into bliss: hence it is said that baptism opens the gate of heaven.

One and the same thing can be generated only once: therefore, as Baptism is a spiritual generation, one man is to be baptised only once. The infection that came through Adam defiles a man only once: hence Baptism, which is directed mainly against that infection, ought not to be repeated. Also, once a thing is consecrated, so long as it lasts, it ought not to be consecrated again, lest the consecration should appear to be of no avail: hence Baptism, as it is a consecration of the person baptised, ought not to be repeated.