"You shall celebrate on your holiday - you, your son, your daughter, your male and female slave, the Levite, the stranger, the orphan, and the widow that are within your gates. Seven days you shall have a holiday to Hashem your God in the place Hashem shall chose, Hashem your God having blessed you in all your produce and all your handiwork, and you shall be 'ach sameach' ". (Devarim 16:14-15)
The beginning and end of the above excerpt, which I have put in bold, form a popular song now sung on holidays. Of course, it is ironic what the song has done to the middle of the excerpt. The Torah made a point of INCLUDING the poor and marginalized members of society in our celebration, but the song jumps over those words, as if to EXCLUDE them! There is always the excuse that long lists of names have no rhythm and are hard to fit to a tune. Granted, but it is still quite striking how the point of the verse has been missed.
Anyway, let us switch from social to philological commentary. The verse ends with the cryptic phrase "vehayita ach sameach". What does this mean, and how does it differ from simply "vehayita sameach"?
Normally, the word "ach" means "but" - introducing a new phrase which qualifies or limits the previous phrase. Here, the word "ach" is not attached to any other phrase, but nevertheless, Chazal understood it to mean "but" in the since of limitation. Since it is never specified WHAT the limitation is, Chazal and later commentators provided a number of suggestions. Among them: 1) Shemini Atzeret may be limited in its degree of "simcha" relative to Sukkot (this assumes that the point of the verse "vehayita ach sameach" as a whole is to teach us that Shemini Atzeret also has a mitzvah of simcha). 2) Even a person without family must perform the mitzvah of simcha, though he cannot do so in the full sense described here (i.e. with sons and daughters). 3) Happiness in this world is limited, in contrast to the World to Come, where it will be unlimited.
Ramban, though, provides a completely different understanding of the phrase. In his commentary to Devarim, he suggests that "ach" is a short version of "achen", meaning "indeed". Thus the phrase means "you shall indeed be happy". It is not a limitation on the holiday happiness, but rather a intensification and expansion of the happiness. Quite the opposite of what Chazal said!
Which of these two contrasting understanding is correct? The advantages of each are clear. Chazal's understanding better fits with the normal meaning of the word "ach". But only Ramban's understanding allows for the sentence to be fully comprehensible and grammatical. Is there an possible understanding which combines both of these advantages - the comprehensibility and the correct usage of the word "ach"?
I think the answer to this question comes from another short and underrated word - "aval". The words "ach" and "aval" are both popularly understood to mean "but". But the word "aval" can also mean "indeed", as it does in Breishit 42:21. There, Yosef's brothers say to one another: "Indeed, we are guilty regarding our brother, in that we saw his distress when he begged us and we did not listen; surely his blood is now being avenged." It makes no sense for the "Indeed" at the beginning of the phrase to mean "but", since it does not come after any other phrase. However, in other places, including modern Hebrew, "aval" does mean "but".
We are forced then to say that "aval" can mean both "indeed" and "but". Perhaps, then, the same is true of "ach"? This allows for an elegant answer to our original question. Chazal are correct that "ach" usually means to take something away, while Ramban is right that in this instance we are commanded to "indeed" be happy.
Indeed (no pun intended), the use of one word for both "but" and "indeed" is not so strange. The roles of those two words in language are not in fact so different. Both typically come after a complete sentence, and add onto the sentence by emphasizing a previously ignored but quite relevant fact. With "but" the new fact serves to limit the previous sentence; with "indeed" it strengthens the previous sentence. This is a difference, but (no pun intended) the correct meaning of the two is easily inferred from context, so there is little confusion in using the same word for both.
Hopefully now we have solved the puzzle of the well-known phrase "vehayita ach sameach". And I'm sure you'll agree with me that my limiting myself to but two unintended puns in this post was impressive, indeed.