1) They apply universally, to Jew and non-Jew alike;
2) They admonish the Jew not to act as a hypocrite; to be pious in public and a sinner in private, against his fellow Jew and Hashem.
A second question is why did the Torah omit mention of Amen as part of the bracha, proclamation? In many places, the Talmud uses the term mushba v’omed m’har sinai (our obligation stems from our original oath taken at Mount Sinai).
Though we are obligated to keep the Torah because it is the will of Hashem, we also took an oath at Mount Sinai to keep the Torah. Where does the Torah mention this oath? Na’aseh v’nishma proclaimed by the people at Mount Sinai did not constitute an oath to keep the Torah in perpetuity. Rather, the oath was accepted by the people, on the last day of Moshe’s life, when he administered it to them as related in Parshas Nitzavim (29:9-14). The oath binding the people to keep the Torah that Moshe administered at the end of his life included that generation as well as all subsequent generations of Jews, es asher yeshno po v’es asher eynenu poh (29:13-14).
However, that oath was imposed on the people by Moshe. Hashem also wanted the Jews to accept the covenant of their own accord. There are many oaths that can be imposed on a person. For example, there are oaths taken regarding the veracity of one’s testimony (shvuas eydus), or regarding the safekeeping of an entrusted object (shvuas hapikadon).
These imposed oaths fall under the category of mushba m’pi acheyrim, accepting an oath administered by others, even against one’s own personal preference. The one obligated does not even have to answer amen to indicate acceptance of these types of oaths.
The people were forced to accept the oath administered by Moshe in Nitzavim, as the Torah says “l’ovrecha b’vris Hashem Elokecha,” you will pass through the covenant of Hashem and accept the responsibility to keep His Torah. We find a similar situation at Sinai, where Hashem suspended the mountain above the heads of the embryonic Jewish nation, pending their acceptance of the Torah. Such coerced acceptance falls under the category of mushba m’pi acheyrim.
The actual incident of the proclamation of the brachos u’kelalos at Mount Gerizim and Eyval, and the amen response by the Jewish people, occurred after Moshe’s death. The people had to answer amen to show their acceptance of the covenant of their own volition. The response of amen to an oath taken of one’s own accord is characteristic of mushba m’pi atzmo, one who takes an oath of his own free will.
The goal of the ceremony at Mount Gerizim and Eyval was for the Jewish nation to accept m’pi atzman, of their own free will, that which they had previously accepted under coercion, either at Sinai or immediately prior to Moshe’s death. Uncoerced acceptance of this oath had to take place after Moshe’s death and after they entered the Land of Israel to ensure that the land was included as a party to the oath.
In the context of mushba m’pi atzmo, the refrain amen is critical. The term arur does not mean curse in this context, either. It means that “I accept as an oath.” In the jargon of Nedarim, laws pertaining to oaths, the term arur is used in conjunction with accepting an oath to refrain from something, for example, arur introduces the self-imposed restriction to refrain from eating something.
We now understand why the Torah emphasized the arur aspect and not the baruch aspect in Parshas Ki Tavo. Many times Hashem promised the Jewish people that they would receive His blessings if they comply with the Torah. From the bracha perspective, not keeping the mitzvos could be viewed as simply nullifying the reciprocal relationship that brings blessing in return for mitzvah observance. However, the arur aspect brings a new and very important dimension to the obligation. By answering amen to the prohibitions of arur, they were no longer only mushba m’pi acheyrim (from Hashem and Moshe), they entered a new level of obligation as defined by mushbain m’pi atzman, accepting the Torah of their own volition, especially the consequences for not keeping its laws.