Astrology for Rationalists

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Nuanced scholars evade simple typologies. Even if they can be broadly described by an intellectual trend, their specific positions sometimes fall outside the expected outcome. This is not a fault of the scholar but of the description, which is often too general to fit any single person. Inconsistency is only a problem if the intellectual structure that demands consistency is artificially imposed by later hobgoblins.

A prime example can be found in the debate among medieval Jewish rationalists regarding astrology. Philosophically and scientifically inclined people of the time widely accepted Aristotelian cosmology, in which the planets and constellations were living beings that affected the happenings in the world. However, many did not take the next step to astrology — believing that people can predict the future by interpreting the locations of the heavenly luminaries. This additional belief hardly seems rational to us yet respected rationalists like R. Avraham Ibn Ezra adopted it. He even wrote a number of books on the subject. And in response, other respected rationalists like Rambam denounced it as foolishness.

In his Iggeres Teiman (ch. 3, p. 42 in the Kafach edition), Rambam states that he infers a belief in astrology from his correspondent’s words. Rambam instructs him to wipe such ideas from his mind because they are demonstrably false:

I note that you are inclined to believe in astrology and the influence of the past and future conjunctions of the planets upon human affairs. Dismiss such notions from your mind. Cleanse your mind of them as one cleanses dirty clothes. Accomplished gentile and certainly Jewish scholars refuse to believe in the truth of this science. Its postulates can be refuted by real proofs on rational grounds, but this is not the place to enter into a discussion of them. (Halkin translation, p. 116)

Note Rambam’s appeal to both truth and expert opinion. Prof. Abraham Halkin, in a note to his translation (p. 142, n. 178), implicitly reduces the effect of Rambam’s appeal to authority: “Maimonides was one of the few in the Middle Ages, Jews or non-Jews, who rejected astrology, and he tried hard to disprove it.” Rambam would surely have responded that the few true scholars deny astrology and those who do not, are not. (Rambam also wrote an entire letter devoted to rejecting astrology. See R. Yitzchak Sheilat ed., Iggeros Ha-Rambam, vol. 2 p. 474ff.)

In a powerful and revealing footnote (n. 54), R. Yosef Kafach — himself a rationalist — discusses his personal struggle with astrology. When he was young, he studied books on the subject and even wrote a commentary to a medieval rabbinic treatise on astrology. On the one hand, like Ibn Ezra, he desired to understand the hidden secrets of the world. On the other, like Rambam, he was unimpressed with the discipline’s intellectual foundation. I would like to think that he overcame his Ibn Ezra-like attraction and adopted a Maimonidean rejection, but I recognize that no one — not even Rambam nor his intellectual descendants — fits nicely into preconceived categories.

About Gil Student

Rabbi Gil Student is the Editor of, a leading website on Orthodox Jewish scholarly subjects, and the Book Editor of the Orthodox Union’s Jewish Action magazine. He writes a popular column on issues of Jewish law and thought featured in newspapers and magazines, including The Jewish Link, The Jewish Echo and The Vues. In the past, he has served as the President of the small Jewish publisher Yashar Books and as the Managing Editor of OU Press. Rabbi Student has served two terms on the Executive Committee of the Rabbinical Council of America and currently serves as the Director of the Halacha Commission of the Rabbinical Alliance of America. He serves on the Editorial Boards of Jewish Action magazine, the Journal of Halacha and Contemporary Society and the Achieve Journal of Behavioral Health, Religion & Community, as well as the Board of OU Press. He has published five English books, the most recent titled Search Engine volume 2: Finding Meaning in Jewish Texts -- Jewish Leadership, and served as the American editor for Morasha Kehillat Yaakov: Essays in Honour of Chief Rabbi Lord Jonathan Sacks.


  1. For those interested, the Wikipedia article has a helpful summary (and uses the same image of the mosaic from the synagogue in Beit Alpha):

  2. I’m not sure of your point. Does it apply to the Rambam at all? Or to R’ Kapach? Neither of them seemed to be both rationalist and astrologist at the same time.

    As to the Ibn Ezra and others, remember that in that time, astrology *was* science, much as the four humors were, or phrenology later. (Or “metaphysics,” for that matter, or “natural philosophy” to take the opposite tack.) Ridiculous science, to be sure, as we now know, but there was no real contradiction back then.

    As to illustrations, you could also have used the beautiful brass inlay zodiac (complete with a rather explicitly nude Virgo and Neptune [also nude] for Aquarius) in the entrance to the main building at YU. Sadly, it’s only uncovered for special occasions, which makes sense. I remember it was once used on a yearbook cover, with R’ Ahron Soloveichik’s permission.

    Of course, the presence of Neptune is a discussion for the chess piece thread. But let us simply point out that the none of the gedolim at YU when the building was built, or in the subsequent nine decades plus, have ever had a problem with it.

  3. The point seems to be a jab at those (Slifkin?) who want to divide Jewish thinkers cleanly between mystics and rationalists.

  4. Yohushea meir

    With the advent of computers astrology has been prover statisticly to be for real and a science.

  5. The point seems to be a jab at those (Slifkin?) who want to divide Jewish thinkers cleanly between mystics and rationalists.

    It’s not a jab at Slifkin. It’s a jab at FK Maniac.

  6. I wrote my above comment in a way which wasn’t so coherent, I’d appreciate it if R’ Gil could delete it. Here’s what I meant to write:

    Valerie Vaughan has written, “Natural astrology referred to a broad, all-inclusive territory of study that encompassed a multiplicity of geocosmic relationships between celestial phenomena and the natural environment of the earth.” It sounds like an area which includes the sort of stuff Rambam was cool with…but then there’s the stuff Rambam came out against. Interestingly enough, it’s not just human affairs that he says are unaffected by the stars: “There is no controversy whatever between the sages of Israel and the philosophers on these matters, as I have made clear in those chapters [in the Guide of the Perplexed, a philosophical treatise]. All three of these sects of the philosophers, which maintain that everything is made by means of the spheres and the stars, also maintain that whatever happens to each and every human being is due to chance; it is not due to any cause coming from above, and neither the constellation under which one is born nor nature will avail against it. There is no difference for them between this individual who was torn to pieces by a lion that happened upon him, or this mouse that was torn to pieces by a cat, or this fly that was torn to pieces by a spider. Neither is there a difference between a roof’s falling upon and killing someone, or a rock’s breaking loose from a mountain and falling upon a tree or upon another rock and breaking it. All this, they maintain, is simply fortuitous.”

  7. The heavenly bodies do affect us. The sun heats us and makes plants grow, the moon moves the ocean. It is a reasonable deduction to say that other heavenly bodies affect us as well. It took modern science to quantify these effects and show that they work only in certain specific and limited ways (i.e. gravity). Even the furthest star affects us through its gravity and illumination, it’s just that now we can calculate that the affect is negligible.

  8. “Nachum on July 8, 2011 at 12:59 am
    I’m not sure of your point. Does it apply to the Rambam at all? Or to R’ Kapach? Neither of them seemed to be both rationalist and astrologist at the same time.”

    Tend to agree with Nachum. BTW-Gil both Nachum andI spell Kapach this way-that is the way he spelt his name in English. Other spellings are scholarly variations of his name in Arabic-Kafih etcsuspect Kafach is a compromise between secular scholars Kafih and Kapach.
    IMHO one can spell ones name anyway one wants-in this case he spelt his name in English as a transliteration of the Hebrew name not the transliteration of the original Arabic.

  9. I agree with R’ Gil that we must follow a path which is reasonable and not adapt to pre-conceived ntions of that which is rationalist or otherwise. This is the approach of Machon Shilo.

  10. 1. The Letter on Astrology is available online here: (I think I read that R. Kapach dispute the authenticity of the letter)

    2. The way the posting is wording, it’s possible to read it as implying the Rambam was reacting to Ibn Ezra. I’m not sure the Rambam knew of Ibn Ezra.

    3. With regard to images of the zodiac, see here in the Ta”z to Yoreh Deah 141 (13)

    4. With regard to “truth and expert opinion”, did the Rambam have empirical evidence that astrology is bunk, and who were the experts on his side at the time that astrology is bunk? I think the Rambam rejected the notion that the heavenly bodies affect the sublunar world simply because it so flies in the face of his conception of hashgachah peratit. But even today many dispute, or at least re-interpret, the Rambam’s views on hashgachah peratit [ie many today believe not a leaf falls by happenstance].

    5. With regard to the closer of “preconceived categories”, I think a gadol is one whose rulings can’t be predicted. Too often we assume Gadol X will rule a certain way because he is from Camp A, and Gadol Y will rule another way because he is from Camp B, and their gadlut is demonstrated when they rule otherwise.

  11. ” Inconsistency is only a problem if the intellectual structure that demands consistency is artificially imposed by later hobgoblins.”

    like the torah or the talmud?

  12. One of the earlier comments: “With the advent of computers astrology has been prover statistically to be for real and a science.”

    This is news to me. Details?

    שבת שלום

  13. I have a question on this week’s parsha which may or may not have a bearing on the subject of astrology:
    I could never comprehend why the curses of Bilam had to be changed to blessings. Had he cursed Israel, would G-d have been forced to effect those curses? What special power did Bilam possess? The Midrash says that Bilam had the power to determine the infinitesimal period of time each day when HaShem is “angry”???, and presumably if the timing of the curse is correct, the curse becomes operative. Can someone explain Bilam’s powers to me?

  14. Nachum: I’m not sure of your point. Does it apply to the Rambam at all? Or to R’ Kapach? Neither of them seemed to be both rationalist and astrologist at the same time.

    In this case, it applies to Ibn Ezra and possibly R. Kafach. In other cases, it applies to Rambam.

    Curious and Observant: You mean I don’t fit neatly into the pro- or anti-Slifkin groups? Truth is, this post is pro-Slifkin but disagreeing with him on the neat division between mystics and rationalists, as I have done before on this blog.

    Melech: The way the posting is wording, it’s possible to read it as implying the Rambam was reacting to Ibn Ezra.

    I believe Halkin suggests that.

  15. Mair Zvi: Isn’t that the Gemara’s question in the beginning of Berakhos? Yodei’a da’as Elyon — he knew the brief moment in the day when God fulfills anyone’s wishes.

    IIRC the Arukh HaShulchan infers from here that when it comes to prayer, as long as your start at the right time the continuation of the prayer is considered as happening at that beginning point. Therefore he allows one to start mincha right before sheki’ah even if your prayer will continue past.

  16. I agree with your point, especially when categories are used in a sloppy way. However, I dont see what your example proves. Both Rambam and Ibn Ezra were “rationalists”. However, at the time, rationalists disagreed about astrology. Hence neither being pro or anti astrology is inconsistent with being a rationalist.

  17. “Observant” said this post is a jab at FKM.

    Indeed, Reb Gil commented on Rabbi Kornreich’s blog that it inspired to to post this in disagreement(which is what brought me here).

    But Rabbi Kornreich is also pointing out subtleties in what aspects of astrology the Rambam upheld. Precisely what point is Reb Gil jabbing at?

  18. Mair Zvi: I believe that it’s a machloket Rishonim if magic is bunk and illusion, or if there’s substance to it, that is to say, if we can’t do magic b/c it’s bunk, or it has substance but we nevertheless can’t do magic.

    As for Bilam, Nechama Leibowitz talks to the issue of who cares what some nonJew curses since it’s meaningless in Studies in Babidbar, Balak 4: The Impact of Curse and Blessing.

  19. “Truth is, this post is pro-Slifkin but disagreeing with him on the neat division between mystics and rationalists, as I have done before on this blog.”

    which I think is exactly what I said:

    “The point seems to be a jab at those (Slifkin?) who want to divide Jewish thinkers cleanly between mystics and rationalists.”

    I was just trying to help those who didn’t get this point, not being critical at all.

  20. Natan Slifkin

    For the record, I have never claimed that there is a neat division between rationalists and mystics. Just that these are two different approaches to Judaism. And the fact that Rambam believed that the spheres exert influence in no way removes him from being a (medieval) rationalist.

  21. That Aish article attempts to redate the Deir Alla inscription to fit better with the incorrect chronology of Chazal. In reality, Jeroboam II reigned in the mid-8th Century BCE, so no redating is necessary. The author “neglects” to tell his audience, in the midst of a “scholarly” piece, that he’s using a very non-scholarly dating system.

  22. Glad to see Aish now accepts the accuracy of carbon dating.

  23. >Glad to see Aish now accepts the accuracy of carbon dating.

    It’s post-Flood, you know.

  24. Ah. Right. Of course.

  25. I don’t think people here (with the exception of Rabbi Lampel) are appreciating how much the Rambam believed in the influence of the stars over the entire planet earth.

    To quote from the Moreh Book II Chapter 10:

    In like manner our Sages say, “There is no single herb below without its corresponding star above, that beats upon it and commands it to grow.” Comp. “Knowest thou the ordinances of heaven? Canst thou set the dominion thereof in the earth?” (Job xxxviii. 33). The term mazzal, literally meaning a constellation in the Zodiac, is also used of every star, as may be inferred from the following passage in the beginning of Bereshit Rabba (chap. x.): “While one star (mazzal) completes its circuit in thirty days, another completes it in thirty years.” They have thus clearly expressed it, that even each individual being in this world has its corresponding star. Although the influences of the spheres extend over all beings, there is besides the influence of a particular star directed to each particular species; a fact noticed also in reference to the several forces in one organic body; for the whole Universe is like one organic body, as we have stated above…

    …The following are the four principal forces directly derived from the spheres: the nature of minerals, the properties peculiar to plants, the animal faculties, and the intellect. An examination of these forces shows that they have two functions, namely, to produce things and to perpetuate them; that is to say, to preserve the species perpetually, and the individuals in each species for a certain time. These are also the functions ascribed to Nature, which is said to be wise, to govern the Universe, to provide, as it were, by plan for the production of living beings, and to provide also for their preservation and perpetuation. Nature creates formative faculties, which are the cause of the production of living beings, and nutritive faculties as the source of their temporal existence and preservation. It may be that by Nature the Divine Will is meant, which is the origin of these two kinds of faculties through the medium of the spheres.

    The question that no-one seems to want to ask is: why is the Aristotelian form of astrology– accepted by Chazal and the Rambam –considered a rationalistic belief (or at least consistent with rationalism) but the more populist form of astrology governing the fate of human beings–rejected by Chazal and the Rambam– considered non-rationalist?

    Was there any empirical evidence for the former and not for the latter?
    I will be developing this question in future posts (on the blog which-must-not-be-named) which will reveal a certain pattern of bias of certain academics regarding their casting of the Rambam as a quintessential rationalist. (Pun intended)

  26. On the topic of the Deir Allah fragments mentioned in the Aish article, the consensus in a shiur on shabbat was that this is the only non-Jewish tanach-era archeological find that mentions a specific torah [as opposed to Na”ch] personality.

  27. FTR, I raised Deir Alla in response to Mair Zvi on July 8, 2011 at 8:34 am. An exploration of the readily accessible sources will make the connection clear.

    I note there is an image of the Deir Alla artifact in Da’at Mikrah (but, I did not have time to look for the corresponding text).

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