On our daf, we discuss the minimum amount of something one needs to transfer on shabbos in order to be liable to punishment.

The  previous Mishna taught us a general rule that something needs to be in a useful quantity  ( worth putting away or כשר להצניע ) in order to cause liability, which fits in well with the concept in general of מלאכת מחשבת , although it should be noted that prohibitions generally come with a minimum שעור    (measurement) that causes liability , not just shabbos prohibitions and these measures are derived from verses and/or oral tradition (הלכה למשה מסיני  עירובין ד.)

It should also be noted that although one is not liable to the prescribed punishment for a transgression that involves less than the minimum amount, we hold that it is still  biblically forbidden to perform such  a transgression  with less than the minimum measurement(חצי שעור אסור מן התורה ) 

When it comes to transferring wine on shabbos, the minimum amount the Mishna requires to be liable to punishment is “the amount required to mix a cup with.”

Wine was generally very potent and thus diluted before use, and the amount required to mix with water to make up one drinkable cup of wine was considered useful or important enough to make one liable for carrying it.

But what size cup are we dealing with?

The Gemara brings a Beraisa which says that it is referring to a minimum size כוס של ברכה , the cup used for  ברכת המזון (the blessings after a bread meal.)

Seeing that after dilution, the cup needs to contain a reviis of the mixed product (etween 86 and 150 ml depending on which opinion is followed ), a quarter of a reviis is sufficient for this .

Not only was it normal to dilute wine before drinking, but Rava was off the opinion that if the wine was not diluted properly , it is not considered wine at all.

This requirement is also the view of Rabbi Eliezer expressed in a Beraisa in שלושה שאכלו  (Brachos 50a)

Yet near the end of the same perek  (Brachos 52a ), we are told  by Rabbi Yochanan that the כוס של ברכה  has a number of requirements, one of them being that it should be “חי ” ( live or undiluted)

How do we reconcile that with our Gemora which clearly says that the wine not only should be diluted 3 to 1, but needs to be?

One possibility, brought by Rashi there, and quoted by Tosfos on our daf, is that the wine only needs to be undiluted when poured into the cup, but after that, it can and should be dilute.

The weakness of this answer is that the word “חי” is now not referring to the cup at the time of the blessing, but only at the time it is poured.  We would then need to prove that it is already considered a כוס של ברכה  from the time of pouring ( and what if he poured it for something else, diluted it, and then decided to use it for כוס של ברכה? The כוס של ברכה  cannot be פגום  (blemished) but being poured for the sake of כוס של ברכה doesn’t appear to be one of the requirements listed in Brachos …) 

An alternative answer brought by Tosfos is that “חי” means partially diluted as opposed to fully diluted, not completely “neat.” Tosfos brings an example of such usage from the law of the בן סורר ומורה (rebellious son), who is only liable if he drinks a certain quality of undiluted wine, yet it is taken there to mean partially diluted.

The initial ברכת הזמון is thus said on a only partially diluted cup which qualifies as חי, after which it is further diluted in the correct quantity.

Yet another answer brought by Tosfos from the sages of Narbonne, is that “חי” in this context does not mean “undiluted ” but rather whole or complete, in a similar way that eating an ant whole ( as opposed to crushed up) is referring to as חי , in the context of דין בריה ( the rule that one is liable for eating a complete forbidden creature even if it is smaller than the usual required quantity for liability ( a kezayis)

What is interesting is that in all 3 answers, Tosfos  seems to take  Rava’s requirement  that the כוס של ברכה be diluted at 25% wine and 75% water as authoritative in all situations , and leaves the Beraisa in Brachos about it needing to be חי subject to interpretation and limitation.

What should we do today? How much stronger was their wine really compared to ours, and how does that affect the halocho?

It seems logical that a weak 6% alcohol wine certainly does not require diluting, but what about a strong wine with 14% alcohol?

Even if their wine contained as much as 28% alcohol, more like our whiskies, 14% should then surely require at least 50% dilution?

Is it even possible to have wine that is 56% alcohol?  Does it depend only on alcohol percentage but also on age?

and who would really want to ruin a good merlot by diluting it?