"The last is Matrimony, instituted to the end that, by means of the legitimate and holy union of man and woman, children may be procreated and religiously educated for the service of God, and for the preservation of the human race."
"Matrimony, according to the general opinion of theologians, is defined: The conjugal union of man and woman, contracted between two qualified persons, which obliges them to live together throughout life. "
"...a perfect marriage has all the following conditions, -- namely, internal consent, external compact expressed by words, the obligation and tie which arise from the contract, and the marriage debt by which it is consummated; yet the obligation and tie expressed by the word union alone have the force and nature of marriage. "
"The special character of this union is marked by the word conjugal. This word is added because other contracts, by which men and women bind themselves to help each other in consideration of money received or other reason, differ essentially from matrimony. "
"The words, which obliges them to live together throughout life, express the indissolubility of the tie which binds husband and wife."
"As grace perfects nature, and as that was not first which is spiritual, but that which is natural; afterwards that which is spiritual, the order of our matter requires that we first treat of Matrimony as a natural contract, imposing natural duties, and next consider what pertains to it as a Sacrament."
The Motives And Ends Of Marriage
"We have now to explain why man and woman should be joined in marriage. First of all, nature itself by an instinct implanted in both sexes impels them to such companionship, and this is further encouraged by the hope of mutual assistance in bearing more easily the discomforts of life and the infirmities of old age. A second reason for marriage is the desire of family, not so much, however, with a view to leave after us heirs to inherit our property and fortune, as to bring up children in the true faith and in the service of God."
"A third reason has been added, as a consequence of the fall of our first parents. On account of the loss of original innocence the passions began to rise in rebellion against right reason; and man, conscious of his own frailty and unwilling to fight the battles of the flesh, is supplied by marriage with an antidote by which to avoid sins of lust."