Q: Under what circumstances does the Torah allow alcohol consumption?
Drinking alcoholic beverages is positive only in very small quantities, for the sake of being able to open up to relate happily and lovingly to another individual. The context of this in Jewish tradition is in a sacred meal or gathering, in which friends sit together in an atmosphere of friendship and holiness and discuss Torah and Chassidic thoughts. At these gatherings, a small amount of alcoholic beverage is consumed in order to open the hearts. This helps one to relate lovingly to his brethren and to reveal to himself the inner dimensions or strata of his consciousness, so that he may learn to better serve God. If this is not the effect of the drinking, it is absolutely prohibited and negative. This is especially true for young people, for whom drinking is not recommended.
The Lubavitcher Rebbe famously limited the amount of liquor that one should drink at a farbrengen to 3 to 4 shot glasses.
