The Chasam Sofer [Yo"d 317] brings the question of the Tshuva Mei-Ahava that the Gemara excludes [at the end of Nazir] a גוי from the din of מופלא הסמוך לאיש [which would make his Nedarim and Erchin count even before he reaches actual adulthood]. From this it would seem that objective shiurim DO apply to Bnei Noach - thus necessitating the exclusion?! [Because if their shiur depends on דעת then there is no מופלא הסמוך לאיש which implies an age - not דעת].
He answers that we say דון מינה ומינה - not only do we learn the general din of Nedarim for בני נח from the law as it applies to Jews, but we learn the details from the Jews as well. So normally they don't have a set shiur of gadlus but for the purposes of Nedarim they do.
ולק"מ בודאי בכל דיני' הנוהגים בב"נ ובכל עניניהם אין מקום לשיעורים דהל"מ הם ולישראל נאמרו ולא לב"נ אך הא נדרי' ועירוכי' איננו ממצות ב"נ אלא התורה חדשה איש איש לרבות ב"נ שנודרים נדרים ונדבות כישראל, א"כ מסתיין כישראל. לא מיבעי' למ"ד דון מינה ומינה דון נדר מישראל ומינה מה להלן בזמנו ובשתי שערות הכא נמי כן אלא אפילו אי בעלמא דון מינה ואוקי באתרי' היינו אי הוה כתיב בחד קרא ישראל ונכרי והוה מקשי' נכרי לישראל אבל נכרי לא כתיב ומאן דכר שמי' אלא איש כתיב ואוקמי' מרבוי' עוד איש אחר היינו נכרי כמו האיש הישראל ודוקא כשהבי' ב' שערות בזמנו וממעטי' התם מופלא סמוך לאיש וכל זה לענין נדרים ועירוכי' אבל לכל דיניהם וקניניהם לא ניתן להם שיעורים ומשבאו לכלל דעת דמסברו לי' ומיסבר הרי הוא גדול.
Now if a גוי becomes an objective gadol when he attains דעת then how can we say דון מינה ומינה? Even for a Jew the דיני נדרים all depend on whether he is a gadol or a year before he becomes a gadol [מופלא הסמוך לאיש]. So we should say the same for a גוי, that a year before he becomes a gadol, his Nedarim take effect - just like for a Jew?!
But if we say [the second approach we suggested] that the גוי is objectively a gadol at 13, just regarding his dinim he is already obligated when he attains דעת, we can say that Nedarim are an exception [because of דון מינה ומינה] and there the determining factor is being a gadol as by a Jew.
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The Gemara says as follows:
אמר רב יוסף הגדילו יכולין למחות איתיביה אביי הגיורת והשבויה והשפחה שנפדו ושנתגיירו ושנשתחררו פחותות מבנות שלש שנים ויום אחד כתובתן מאתים ואי ס"ד הגדילו יכולין למחות יהבינן לה כתובה דאזלה ואכלה בגיותה
Rav Yosef said: In any case where minors convert, when they reach majority they can protest and annul their conversion. Abaye raised an objection to his opinion from the mishna: With regard to a female convert, or a captive woman, or a maidservant who were ransomed, or who converted, or who were freed when they were less than three years and one day old, their marriage contract is two hundred dinars. And if it enters your mind to say that when they reach majority they can protest and annul their conversion, do we give her the payment of the marriage contract that she will go and consume in her gentile state?
לכי גדלה לכי גדלה נמי ממחייא ונפקא כיון שהגדילה שעה אחת ולא מיחתה שוב אינה יכולה למחות
The Gemara answers: She receives payment of her marriage contract once she has reached majority and does not protest, but not while still a minor. The Gemara asks: When she reaches majority too, is there not the same concern that she will protest and abandon Judaism? The Gemara answers: Once she reached majority for even one moment and did not protest, she may no longer protest. This mishna poses no difficulty to the opinion of Rav Yosef.
The Shittah Mekubetzes says that "הגדילו" means that she is בר עונשין [i.e. 12 for a girl, 13 for a boy]. The Tosfos Ri"d says that "הגדילו" means that they have דעת. But this is not a contradiction to what we are saying that for קבלת גירות we require that he reach the age of עונשין [i.e. 13 and therefore in order for a קטן to convert he needs דעת בית דין - not like Rav Aharon who said that once reaching the age of דעת he can convert מדאורייתא]. Just as far as מחאה is concerned it is sufficient that he reach the age of דעת because in order for a 13 year old to convert he also needs a desire to convert [as the Tos' Ri"d writes] and if he lacks that desire he is not a ger. So if he protests after achieving דעת and shows a desire not to be Jewish, he reverts back.
However when the Gemara says "כיון שהגדילו שעה אחת ולא מיחו שוב אין יכולים למחות" - that means that from the time they become בר עונשים they can no longer protest because what [revents the מחאה is that they reached the age of gadlus and עונשים [i.e. 13]. So that means that they have the right to protest their conversion from the age of דעת until 13.
That would solve a big problem. Tosfos Yeshanim wonders when the מחאה takes place. As long as she is a קטנה the מחאה is ineffective and the when she becomes a גדולה it is again ineffective. So when is that magical moment/s when she can protest? Tos' Yeshanim answer that she can protest from when she is at the end of her קטנה period through her transition into גדלות. But our explanation solves the problem because it enables her to protest from the time she attains דעת until she reaches the age of עונשים. [In the glosses on the Tos' Ri"d he says that with the explanation of the Tosfos Ri"d, we can answer the question of the Tosfos Yeshanim. That would work based on our understanding of the Tos' Ri"d.
Rashi [ד"ה הגדילו] writes "אם קידש אשה משמיחה אין צריכה גט" that if he was מקדש an אשה, after the מחאה she doesn't require a get. This means that first he was מקדש the אשה and then protested, she doesn't require a get. How can this be? When he was מקדש her after he became a גדול, that is an expression of his acceptance of Judaism, so his מחאה is AFTER THE BUZZER. Too late!!?
But based on what we said, the scenario would be that he attained the דעת of a Ben Noach a number of years after reaching the age of the gadlus of a Jew [13]. So his Kiddushin is valid as a full fledged Jew but he reserves the right to protest until he reaches the level of דעת for a בן נח, for as we explained, in order to be a willing convert, one needs דעת of a בן נח. Such a protest would indeed uproot the Kiddushin obviating the need for a get.
[עפ"י תורת הג"ר שמעון משה דיסקין זצ"ל]
