Reprinted from the introduction to Fundamentals and Faith, by Rabbi Yaakov Weinberg (Targum Press).
It should be stressed that all Torah scholars agree on the validity and significance of the Principles. However, some of the Rambam’s [Maimonides’] contemporaries questioned whether a lack of awareness of or belief in several of the Principles would result in an actual estrangement from Judaism.
The Raavad [Rabbi Abraham ben David of Posquieres], for example, says that although it is foolish and incorrect to take the Torah’s reference to the "hand of God" literally, those who believe God to be corporeal can still relate to Torah as members of the Jewish community.
Other Rishonim [medieval Talmudic scholars] maintain that the Jew raised among the gentiles [the traditional example of a Jew who may not be responsible for his religious negligence] can still fulfill mitzvos [commandments], even if he is not aware of God’s promise concerning the coming of the Mashiah [the Messiah].
Granted, the educated and learned Jew who denies that history will culminate in the coming of the Mashiah is an apikorus [a heretic] and has estranged himself from Judaism, but the ignorant individual, they say, whose beliefs do not include the Mashiah, can still keep Shabbos and observe the laws of kashrus; he can live in a sukkah [on the holiday of Sukkot] and eat matzah on Pesach. Despite his ignorance, he remains part of the Jewish community.
The Rambam disagrees. He states that without the understanding and awareness of the Mashiah, the Shabbos that an individual keeps or the laws of kashrus he fulfills are performed as an estranged Jew who is not part of the community of Israel. Such an individual’s approach to the mitzvos and his understanding of the nature of his commitment lack a basic element.
In general, all of the various disputes regarding the Thirteen Principles are of this nature, concerned not with the validity of the Principles but with the consequences of not knowing or believing them.