The level of drunkenness affects a person’s vow TB Nazir 11

Clearing up a contradiction in the Mishna, the Gemara on daf TB Nazir 11 provides the context. “If they poured a cup of wine for one and he said: I am hereby a nazirite and therefore will refrain from it, he is a nazirite. And if he is intoxicated and they pour a cup of wine for him and he said: I am hereby a nazirite and therefore will refrain from it, he is not a nazirite. What is the reason for this? He is considered to be like one who said: This cup is forbidden to me like an offering. The Gemara asks: And if you would say that this was his meaning, let him say so explicitly; why would he say: I am hereby a nazirite and therefore will refrain from it? The reason is because he maintains: If I specify this cup, they will bring me another cup and aggravate me with it. It is better that I say to them this statement, which is definitive to them, and they will understand that I do not want to drink any more wine.” (Sefaria.org translation)

In the first case of the story, the man is sober. As soon as he says that he is a nazir, it doesn’t matter that he refrains from this cup of wine. He accepts upon himself all three prohibitions of a nazir, abstaining from grapes and all grape products, from cutting one’s hair, and coming into contact with the dead.

The second case of the story, the man is tipsy from drinking wine. He knows that if he drinks more, he will become truly drunk. Consequently, he phrases his refusal in absolute terms of a nazir so his guests won’t offer him more alcohol. If he just said that this cup of wine is forbidden to him like a sacrifice, his guests might have mistakenly understood that he doesn’t want this cup of wine, but will gladly accept other cups of wine.

Rambam in his commentary on this Mishna adds third level of drunkenness. If a person is as drunk as Lot was, he is not held liable for anything he says. How drunk was Lot? After the destruction of Sodom and Gomorrah, his two daughters thought that the world had ended and they were the only survivors left to populate the world. They got their father so drunk, that he did not know that he had intercourse with them. The daughters became pregnant. One child became the ancestor of the Moabites and the other child became the ancestor of the Ammonites. (Genesis 19:31-38)