[This begins what is planned to be a series of posts on reactions of segments of the Jewish world to the post-Rebbe messianism of the Chabad movement.]
A large number of Chabad defenders contend that, because Chabad is "doing so much good" by "inspiring people to do mitzvot and come closer to Judaism," the theological "quirks" of the movement – like its belief in the "second coming" of the "messiah," the late Rebbe who was while alive, is now in "concealment" or in what "only appears to be death," and will be soon revealed to all as, the messiah – can be overlooked.
The Rebbe, it is argued, inspired a mass return to the practice of traditional Judaism. Someone who has caused this good cannot be the source of evil. Additionally, the Rebbe is followed by thousands of rabbis. Someone with that type of esteemed following cannot be the cause of sin.
The point I am making is not that Shabbatai Tsvi and the Rebbe are to be equated.
The point I am making is this: All the good deeds and the best of intentions in the world do not prove messianship. Only the completion of the specific deeds codified by the Rambam and accepted as halakha (law) can do that.
As the Rambam specifies, these deeds – the ingathering of the exiles, rebuilding of the Jerusalem Temple, and ushering in the era of world peace, among others – must be completed. If the presumptive messiah dies before completing these acts, he is not the messiah promised by the Torah:
"But if he did not succeed [in building the Jerusalem Temple, etc], or if he was killed, he is not this one the Torah promised us – he is instead like all proper and righteous kings of the House of David who died. The Holy One, Blessed Be He, only set him up to test the people by him: "And from the seekers of wisdom there shall stumble, to purify among them and to clarify and to brighten until the time of the ending, for there is yet to the set time" (Daniel 11:35)." [Rambam, Mishneh Torah, Hilkhot Melakhim, Chapter 11.]
This halakha (law) rules out the messianship of Jesus, Shabbatai Tsvi, and dozens of lesser-known Jewish "messiahs." And it rules out the Rebbe, as well – no matter how many Jews he inspired, and no matter how many good deeds he did.