A lot of ink has been splashed about on the Rambam's 13 Principles. Here's a little bit more.
If one thinks about what he didn't include in his list one may come up with things; for example, why isn't belief in am ha-nivchar (Jewish chosenness) a principle? Ikkarei emunah are roots of Judaism; evidently the Rambam did not believe that chosenness was one. The question becomes more acute, I believe, if you accept Marc B. Shapiro's premise in The Limits of Orthodox Theology* that the Rambam's listing of principles are more a matter of what he thought were necessary beliefs** as opposed to [entirely] true beliefs**. If that were the case then the question of why Jewish chosenness would not be a necessary belief is especially noteworthy insofar as it is certainly a fundamental Jewish belief of some sort.
To put it another way, if we assume that according to the Rambam if any one of his ikkarim were to be discarded by the the Jewish people then no less than a pillar of Judaism would be uprooted why is it that am ha-nivchar is not one of them? Could it be that according to the Rambam belief in Jewish chosenness is not necessary for Jewish people? Evidently that is so.
It seems odd. At least it strikes me as odd. Maybe the reason he did not include it is because the supercessionist assertion of Christianity and Islam towards Judaism were perceived by Jews as arrogant and unfounded and only reinforced their own belief in Jewish chosenness.
Thoughts, anyone? Also feel free to share if you can think of an other concept that may have/ should have been given as an ikkar.
*Which does not, by the way, take issue with the factual truth of any of the Rambam's principles, only the assumption that they were universally received by all earlier and subsequent rabbinic authorities.
**A necessary truth would be telling children that crime doesn't pay, even though there is quite a bit of evidence to the contrary.