Sacraments are outward signs of inward grace, instituted by Christ for our sanctification (Catechismus concil. God is not restricted to the use of material, visible symbols in dealing with men; the sacraments are not necessary in the sense that they could not have been dispensed with.But, if it is known that God has appointed external, visible ceremonies as the means by which certain graces are to be conferred on men, then in order to obtain those graces it will be necessary for men to make use of those Divinely appointed means. 4) declared heretical those who assert that the sacraments of the New Law are superfluous and not necessary, although all are not necessary for each individual.Martin Luther's Catechism, the Augsburg, and later the Westminster, Confessions are strongly sacramental in their tone, putting to shame the degenerate followers of those who compiled them" (ibid., p.7, 8) The reasons underlying a sacramental system are as follows: Taking the word "sacrament" in its broadest sense, as the sign of something sacred and hidden (the Greek word is "mystery"), we can say that the whole world is a vast sacramental system, in that material things are unto men the signs of things spiritual and sacred, even of the Divinity.But about the time of Abraham, when faith had been weakened, many had fallen into idolatry, and the light of reason had been obscured by indulgence of the passions, even unto the commission of sins against nature, God intervened and appointed as a sign of faith the rite of circumcision (Genesis 17; III:70:2, ad 1; see CIRCUMCISION).The vast majority of theologians teach that this ceremony was a sacrament and that it was instituted as a remedy for original sin; consequently that it conferred grace, not indeed of itself (), but by reason of the faith in Christ which it expressed.
Afterwards, however, as it was necessary to give a written law: (a) because the law of nature had been obscured by sin, and (b) because it was time to give a more explicit knowledge of the grace of Christ, then also it became necessary to determine what external signs should be used as sacraments (III:60:5, ad 3; III:61:3, ad 2) This was not necessary immediately after the Fall, by reason of the fullness of faith and knowledge imparted to Adam.
This truth theologians express by saying that the sacraments are necessary, not absolutely but only hypothetically, i.e., in the supposition that if we wish to obtain a certain supernatural end we must use the supernatural means appointed for obtaining that end. It is the teaching of the Catholic Church and of Christians in general that, whilst God was nowise bound to make use of external ceremonies as symbols of things spiritual and sacred, it has pleased Him to do so, and this is the ordinary and most suitable manner of dealing with men.