St. Thomas ordered the sacraments this way (Summa Theologica III q. 65 a. 1
We may likewise gather the number of the sacraments from their being instituted as a remedy against the defect caused by sin.
- Baptism is intended as a remedy against the absence of spiritual life;
- Confirmation, against the infirmity of soul found in those of recent birth;
- Eucharist, against the soul's proneness to sin;
- Penance, against actual sin committed after baptism;
- Extreme Unction, against the remainders of sins---of those sins, namely, which are not sufficiently removed by Penance, whether through negligence or through ignorance;
- order, against divisions in the community;
- Matrimony, as a remedy against concupiscence in the individual, and against the decrease in numbers that results from death.
For the first ordering above, he gives this reason (ibid. a. 2
c.): "those sacraments which are intended for the perfection of the individual naturally precede those which are intended for the perfection of the multitude". Also, Holy Orders and Matrimony are last ∵ they are "intended for the perfection of the multitude" and "Matrimony is placed after order, because it has less participation in the nature of the spiritual life, to which the sacraments are ordained." He says Eucharist could be placed before Confirmation, too, because nourishment causes growth. Baptism is so important! Everything is rooted in it!
He also pairs the sacraments with specific virtues (ibid. a. 1
Some, again, gather the number of sacraments from a certain adaptation to the virtues and to the defects and penal effects resulting from sin. They say that
- Baptism corresponds to Faith, and is ordained as a remedy against original sin;
- Extreme Unction, to Hope, being ordained against venial sin;
- Eucharist, to Charity, being ordained against the penal effect which is malice.
- order, to Prudence, being ordained against ignorance;
- Penance to Justice, being ordained against mortal sin;
- Matrimony, to Temperance, being ordained against concupiscence;
- Confirmation, to Fortitude, being ordained against infirmity.