HAD members of the rabbinic profession been aware of Kalischer's letter to Rothschild and his subsequent halakhic correspondence with his teacher Akiva Eger, they would have considered them as acts of boldness. To be sure, Kalischer's literary initiatives involved none of the physical exertion or public rallying usually considered under the rubric of activism. Neither does it seem that there is much room for change when a person is firmly committed to operating within the bounds of the Torah. Yet within the usual constraints of the rabbinic world, Kalischer was actually making a very bold move. He was proposing a revolutionary change in the structure of Jewish life and throwing behind it his authority as a rabbi. Even within the confines of Jewish law there was room to manoeuvre, because rarely in rabbinic literature is a matter ever decided absolutely and with finality. Reviving sacrificial worship had never been absolutely forbidden, and because it was essential to his messianic scheme Kalischer exerted all his halakhic training and creative powers to construct a case for it.

The letter to Rothschild contained Kalischer's technical and highly sophisticated analysis of the halakhic issues involved in resuming sacrificial worship. Clearly the work of many months of research, the analysis would have been comprehensible only to a person with a yeshiva education. In accordance with the centuries-old technique of halakhic argumentation, Kalischer stated and rebutted opposing positions, presented a wide array of proof texts and supporting legal opinions from venerated rabbinical scholars and sacred books, and concluded that the matter was resolved favourably. Anyone who read it, he thought, would be assured that they were free to act upon their desire and obligation to restore the sacrificial cult.

The halakhic analysis that Kalischer included in his letter to Rothschild and that he sent separately to Eger was, on the surface, highly obscure. It dealt with the sanctity of Jerusalem's terrain, the laws of ritual purity, priestly genealogy, and the like. His sacrifice responsum, however, must be seen as operating on two levels: on the surface it was a narrow halakhic analysis of a particular problem of Jewish ritual; on a deeper level, it was his response to the debate on the extent to which Jews controlled their national fate—that is, the issue of realistic or passive messianism.