(Mishnah): The following fruits are obligated in Demai in any place (meaning, even from Kaziv and beyond, which is usually exempt from the laws of Demai)... pressed figs, dates, carobs, rice, and cumin. However, as for rice from Chutz LaAretz (which is visibly different to rice from Eretz Yisrael), whoever uses it is exempt from Demai.

(Gemara): A Mishnah (in Maseches Maaseros) teaches - the following produce is exempt from Maaseros in Eretz Yisrael (because they don't grow in Eretz Yisrael and were certainly brought from Chutz LaAretz) - 'Ba'al Bechim garlic, Richpa onions, Kilakin beans and Egyptian lentils' - since these species (e.g. garlic, onions) grow in Eretz Yisrael, Chazal need to specify the type of each species that is exempt; but as for Altzarin, Pistachin and Itztubolin, since none of those species grow in Eretz Yisrael, there was no need to specify the type.

(R. Avin): Unlike that Mishnah (in Maaseros that listed things that certainly do not grow in Eretz Yisrael), our Mishnah taught that there is an obligation on a species that does not grow in Chutz LaAretz (so it certainly grew in Eretz Yisrael).

Question: Doesn't our Mishnah list pressed figs, even though they grow in Batzrah (which is Chutz LaAretz)?

Answer: The weak ones used for grinding grow in Eretz Yisrael.

Question: Don't dates grow in Alexandria?

Answer: Those are the thin, skinny ones.

Question: Don't carobs grow in Biari?

Answer: There, they are broken, weak ones.

Question: Doesn't rice grow in Chulta?

Answer: There it is round and red.

Question: Cumin grows in Kipros?

Answer: There it is crooked.

(R. Elazar): The law of Demai only applies to produce bought from a Jew (Am HaAretz); but if bought from a gentile, it is definite Tevel.

(R. Yochanan): It makes no difference whether it is bought from a Jew or a gentile; it is Demai.

R. Elazar reasoned that most of Eretz Yisrael is in the hands of gentiles.

R. Yochanan reasoned that most of Eretz Yisrael is in the hands of Jews. (We assume that even when he buys produce from a gentile, the gentile probably bought it from Jews, so it is Demai and must be tithed.) But even if R. Elazar would agree with R. Yochanan about that, he is still concerned for the minority, so produce bought from a gentile must certainly be tithed.

It is like the caravan of travellers who, although on most days they take permitted food, one day they take prohibited food - on any given day we have a doubt and it is considered 'kavua' - a fixed day. Therefore, it is as if this happened on half of the days, making it prohibited. (This is an application of the concept (found in many places, including Bavli Kesuvos 15a, where it is learned from a pasuk) that when the item about which we are in doubt is kavua, meaning fixed or stationary, we do not follow the majority - rather it is viewed as a 50/50 doubt).

Question (R. Yosi): If R. Elazar is concerned for the minority in such a case; if someone wants to convert, we should not allow it since perhaps he is from the nations of Amon or Moav? (Converts from those nations are not permitted to marry into the community.)

Rather, it is as already stated, that R. Elazar reasoned that most of Eretz Yisrael is in the hands of gentiles; and R. Yochanan reasoned that most of Eretz Yisrael is in the hands of Jews.

Further proof: R. Zeira sent a question to R. Alexandria of Tzidoka - these Niklavesin (a type of high quality date) that grow here; what do you say about them? Do most of them grow in the hands of the gentiles or in the hands of the Jews? R. Alexandria answered that he is not able to evaluate them. (The question shows that we follow the majority and ignore the minority.)

R. Elazar and R. Yochanan each have a Baraisa that supports them. A Baraisa that supports R. Elazar - if a person buys from any merchant, it is considered Demai. When is this? When the merchant mostly buys from Jewish farmers, but if he buys from gentiles, it is definitely Tevel.