Bo (Rambam)

Thoughts on the Laws of the New Moon

This week we turn from theological and philosophical issues to an entirely different aspect of Rambam’s work: his scientific interest, specifically his interest in astronomy and the calendar. A unique feature of the Mishneh Torah, found in no other halakhic code, is his extensive treatment of the laws governing the sanctification of the New Moon, presented in a separate, nineteen-chapter section of Sefer Zemanim known as Hilkhot Kiddush ha-Hodesh. This mitzvah, often considered the first proper mitzvah of the Torah, is derived from a verse in these week’s portion in which Moses and Aaron are told together, “This month shall be for you the first [or: head] of the months” [Exod 12:2]. The rabbis infer from this that the High Court (of whom Moses and Aaron are in some sense forerunners) are charged with declaring the new months.

In this treatise, Maimonides describes in great detail the laws by which the Jewish calendar operated in ancient times: namely, the High Court or Sanhedrin sat in the Temple precincts in Jerusalem (after the Destruction, in Yavneh; later still, in various places throughout the Galilee, such as Usha, Tzippori, Shefaram, Bet Shearim, and Tiberias), and people who had witnessed the appearance of the new moon would go there and testify to what they had seen; after examining the witnesses and verifying their testimony, the Court would then declare the New Moon to be “sanctified.” This same body would also deliberate whether or not to add an extra month so as to realign the lunar year of twelve months, which has only 354 days, with the seasons of the solar year.

The presentation of these laws is unique to Rambam, and is but one expression of an overall feature of his Code: namely, that it encompasses all of Jewish law, including those subjects that are inoperative today, such as the laws of the Temple and its sacrifices, rules of ritual purity and impurity, agricultural laws applicable only in Eretz Yisrael, laws of the Sanhedrin and the kings, etc. The other major halakhic codes, such as Hilkhot ha-Rif, Semag, & Arba’ah Turim, do not include these subjects, but studiously omit them.

One reason for Maimonides’ decision to include all these laws was simply the wish to present Torah in an all-encompassing way: if a given topic appears in Scripture and in the Oral Law, then it must appear in his Code as well. As he explains in the Introduction to the Yad, his purpose was to create a handbook which would make the vast material of the Oral Torah accessible to all, without needing to wade through the vast labyrinth of Talmudic and Geonic literature, with their lack of systematic order and multitude of diverse opinions.

Yet there was more to it than that. Maimonides’ consciousness was informed by a deep and fervent messianic longing, which took the ancient kingdom as paradigmatic: the institutions of the Temple, the monarchy, the Sanhedrin, even the presence of prophecy, are all central components in the ideal template, so to speak, of Jewish existence. Even if seemingly not articulated in a passionate or immanent way, a deep longing for redemption and for restoration of the days of old informs everything that Maimonides writes.

But that is only half the story. If Rambam were only interested in presenting the procedures followed by the Great Court in sanctifying the new moon and intercalating months to make leap years, as described in Tractate Rosh Hashanah—in much the same way as he codifies other laws that he would no doubt describe, not as defunct, but as “in long term abeyance”—he would only have needed those five first chapters of Hilkhot Kiddush ha-Hodesh that are devoted to halakhic matters per se.

What makes this treatise sui generis are the remaining fourteen chapters, constituting the bulk of the treatise, that are devoted to another concern, best described as scientific rather than halakhic. Already in the beginning of this treatise he makes the statement that the Sages, in addition to waiting for eye witnesses to the new moon to show up in Court, had an alternative, mathematical “backup” system for determining when the New Moon would occur: what is known as sod ha-ibbur—the secret of the “gestation” of the New Moon. This concept is alluded to at one place in Talmud, at the very top of Rosh Hashanah 20b, with the intriguing gloss by Rashi that it as an esoteric work, “taught by allusion” (beraita shenuyah beramazim). In other words, according to Rambam, the entire procedure of receiving and questioning witnesses, showing them charts, cross-examining them as to which direction the tips of the crescent moon were pointing, whether it was to the north or south of the setting sun, etc., were in a sense superfluous, intended merely to provide formal legal confirmation for something they already knew well through their own mathematical computations. The balance of Hilkhot Kiddush ha-Hodesh is then a detailed reconstruction of what Rambam claims to have been the method used by the Sages to determine the exact time of the New Moon.

I do not know how historically accurate Rambam’s assertion is, nor to what extent this work is the reconstruction he claims it to be. The Talmudic text is sparse. One wonders whether Maimonides may not have projected his own scientific and astronomical knowledge backwards in time, moved by the belief that the Sages must have known what he knew, even in the realm of empirical science. In any event, his whole interest here in the scientific underpinnings of Kiddush Hahodesh clearly reflects his own attitude toward the relation of Torah and science, and his belief that all sources of truth are ultimately reconcilable and even complement and reinforce one another (in much the same way as in the Guide he undertakes great efforts to harmonize Aristotelian philosophy and tradition).

Although I have read this treatise through several times, I must confess that I do not feel that I have read it closely or thoroughly enough to fully understand his scientific argument. Moreover, living as I do at this point in history I cannot help feeling the anachronism in this text. Rambam lived in a Ptolemian universe— Copernicus, Tycho Brahe, and Galileo were all more than three hundred years in the future: a universe in which the sun, the moon, and the heavenly bodies all revolve around the earth. In such a system, it is necessary to introduce numerous corrective factors in order to account for the deviations in the observed motions from purely circular orbits: an entire system of epicycles, of secondary motions of the orbits of, e.g., the moon, the sun and the planets, against a theoretical spherical plane upon which they are fixed. For most of us, who accept the model of modern astronomy, this treatise is of interest more in terms of the history of science than as a useful tool.

It is nevertheless impressive that this faulty theoretical model in no way affected the ability of Rambam and others to precisely observe the movements of the heavenly bodies, and to extrapolate them indefinitely into the future. The traditional Jewish calendar, established on a purely mathematical basis by Rav Hillel in the third century, after the Sanhedrin ceased to function, still works to this day. It has proven itself to be far superior to the Julian calendar, which lost nearly a full day every century—and which was only corrected in the 16th century by Pope Gregory XIII. The Jewish year remains accurate and, even more remarkable, in synch with both the lunar and solar cycles.

I will conclude with a brief illustration to concretize the difference between Maimonides’ understanding of what was involved in declaring the New Moon and that of what might be called the mainstream of halakhic thought. First, the relevant passage from Sefer ha-Hinukh, an enumeration of the 613 mitzot with brief definitions, descriptions, and rationales for each mitzvah, most probably written by R. Aaron ha-Levi of Barcelona in the late thirteenth century, and arranged according to the order of the weekly Torah readings. The fifth mitzvah in Sefer ha-Hinukh is described as follows:

To sanctify new moons and to intercalate years in the Court that is greatest in wisdom, of those that have received ordination in the Land; and to fix the festivals of the year according to that sanctification, as is said “This month shall be for you the first of the months…” [Exod 12:2]

Rambam, by contrast, gives the following heading to Hilkhot Kiddush ha-Hodesh (each section of the Mishneh Torah is preceded by a heading, listing the mitzvot whose laws are contained therein):

There is therein one positive commandment, namely, to calculate and to know ad to fix on which day shall be the beginning of each month of the months of the year.

Note the crucial addition here of the words “to calculate and to know.” For Rambam, the court fulfills not only a formal, authoritative function, stemming from its juridical status (and its being ordained in Eretz Yisrael!), but is also obligated to engage in cognitive—if you will, scientific—activity. “To calculate” implies an active searching out and acquisition of the knowledge needed to do so correctly. The same idea is expressed in the body of the laws, at 1.6-7; but compare also what he says in Sefer ha-Mitzvot, Aseh §153.