From the Supplement, compiled after Aquinas’s death from his Commentary on the Sentences and transcribed here from the 1917 to 1922 printings. About the Supplement.
Text: Summa Theologiae, Supplement to the Third Part (Supplementum Tertiae Partis), transcribed from Internet Archive scans, translated by the Fathers of the English Dominican Province. The Supplement, compiled after Aquinas’s death from his earlier Commentary on the Sentences, in the same English Dominican translation as the Gutenberg Parts. Transcribed by Bibliotheca Catholica from the OCR of four Internet Archive scans of the pre-1931 printings (Questions 1 to 33 from the 1917 Washbourne and Benziger volume, 34 to 68 from the 1922 volume, 69 to 86 from the 1921 volume, and 87 to 99 from the 1922 Benziger volume), with OCR errors corrected and doubtful passages marked, not rewritten. 99 questions and 446 articles. The two appendices printed after Question 99 are not included. Sources, SHA-256 of each OCR file, and the method are in the source record. Rights: Public domain (US)
The Supplement is not a Project Gutenberg text. It is Bibliotheca Catholica’s transcription of public-domain scans at the Internet Archive; obvious OCR errors were corrected, and passages marked “OCR uncertain” could not be confidently corrected, so check them against the linked scan page.
Objection 1: It would seem that not even a conditional consent makes a marriage, because a statement is not made simply if it is made subject to a condition. But in marriage the words expressive of consent must be uttered simply. Therefore a conditional consent makes no marriage.
Obj. 2: Further, Marriage should be certain. But where a statement is made under a condition it is rendered doubtful. Therefore a like consent makes no marriage.
On the contrary, In other contracts an obligation is undertaken conditionally, and holds so long as the condition holds. Therefore since marriage is a contract, it would seem that it can be made by a conditional consent.
I answer that, The condition made is either of the present or of the future. If it is o;f the present and is not contrary to marriage, whether it be moral or immoral, the marriage holds if the condition is verified, and is invalid if the condition is not verified. If, however, it be contrary to the marriage blessings, the marriage is invalid, as we have also said in reference to betrothals (O. XLIIL, A. i). But if the condition refer to the future, it is (uther necessary, as that the sun will rise to-morrow,--and then the marriage is valid, because such future things are present in their causes,--or else it is contingent, as the payment of a sum of money, or the consent of the parents, and then the judgment about a consent of this kind is the same as about a consent expressed in words of the future tense; wherefore it makes no marriage.
This suffices for the Replies to the Objections.
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Also online, linked only: the same translation at New Advent and the Latin text at Corpus Thomisticum. Neither is copied here.