As noted here, the evidence for Judaism is subject to dispute. The most intellectually honest approach to this question would seem to require one to thoroughly investigate the matter and follow his well-researched conclusion. This logic should extend to telling someone to follow his conclusion, even should he conclude, say, Catholicism is true.

However, though some Rishonim provide proofs for Judaism, I have not found any Rishonim echo this claim of mine. Further, they often seem to present these proofs as means of fulfilling the mitzvah of Emunah and perhaps silencing doubts, not as a "neutral" approach (see beginning of Aaliyah's answer in the aforementioned post) to help one clarify whether or not Judaism is correct.

For instance, I have yet to find a Rishon who endorsed a comparative religion study. And yet, this approach would seem to be most honest and sensible to me.


  1. Why is this idea not expressed by the Rishonim? What's wrong with my way of thinking?
  2. Please provide sources if it is.
  • 1
    – shmosel
    Feb 13, 2023 at 4:02
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    I wouldn't be able to find it now, but the Moreh Nevuchim says clearly that if full investigation showed something different (he's talking about the world existing forever) from the current way the Torah is understood, we would of course begin understanding it in that way.
    – MichoelR
    Feb 13, 2023 at 7:30
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    Yehuda, do you not see the flaw in this logic? Jewish sources must be believed first in order to empower them as valid sources for any obligation or permission. Jewish sources can't obligate one to believe, or give valid permission to not believe themselves! One has to already believe in God before one will accept a commandment from Him to believe in Him. Of course then, the Rabbonim assume one believes if one is relying on them already, and thus are not going to entertain the possibility that the Torah can be abandoned.
    – Rabbi Kaii
    Feb 13, 2023 at 11:54
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    @RabbiKaii I think you make an excellent point. I've considered this and I imagine it's most of the answer. Can you post as an answer? Still, consider the following scenario. If your teenage child told you he was struggling with religion and wanted to investigate the matter, and he asked you if this decision to investigate is his moral right, how would you respond? I'm not sure how I would respond. But a large part of me would acknowledge that it is, and would not only see it as his moral right but as his moral obligation (despite the fear it would engender for me).
    – Yehuda
    Feb 13, 2023 at 13:49
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    @MichoelR Thank you, that is fascinating.
    – Yehuda
    Feb 16, 2023 at 0:56

3 Answers 3


Why is this idea not expressed by the Rishonim? What's wrong with my way of thinking?

The idea isn't expressed in Rishonim due to the intrinsic problems with studying heresy. See the last perek of Sanhedrin and the second perek of Chagiga for more detail.

What's wrong with the way of thinking is that history has shown that is doesn't work. As the Gemora says (when discussing the prohibition of delving into it) "heresy is compelling" That is true regardless of what the heresy is actually saying.

Thousands of years of Jewish history has shown that those who go off OTD claiming to be truth seekers who couldn't find answers in Orthodox Judaism have almost always ended up believing whatever was preached by the intelligentsia or the masses of the time and place they happened to have found themselves in. Makes no difference whether they believed in. Could have been Catholicism, Islam, idolatry the world has always existed etc. etc. etc. the belief varied greatly, the claim of "as a truth seeker I can't avoid this conclusion" remained constant and unchanged. Another thing that remain unchanged was that the "truth seekers" only flourished in societies that allowed free entry to the upper middle class. Otherwise the OTD movements preached an anti establishment message. Because the host culture only wins over believers when they are offering something in return.

Therefore the results of telling people to study comparative religion (and presumably atheism) for the sake of intellectual honesty is just going to be mass assimilation to their host culture. Also for ostensible "intellectual honesty"

That said the Mishna in Pirkey Avos 2:14 says וְדַע מַה שֶּׁתָּשִׁיב You do need to know what answer heretics. Not just brush them away with "they don't know what they are talking about"

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    Great answer. You left out a big one: communism! And on your last paragraph, see this comment: judaism.stackexchange.com/questions/132813/…
    – Rabbi Kaii
    Feb 13, 2023 at 14:35
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    Communism was included in the anti establishment movements that took off in societies that wasn't allowing entry to the upper middle class anyway
    – Schmerel
    Feb 13, 2023 at 14:45
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    @Schmerel Thanks for the superb answer. You've explained the problem (both religious and practical) with societal engagement in studying heterical subjects for "the sake of truth-seeking". But the alternative is also quite difficult- how can someone honest believe if he doesn't feel he has done an honest investigation? Also, do you think it's humanly possible to overcome these biases?
    – Yehuda
    Feb 13, 2023 at 15:40
  • That is an issue but it is a universal and circular one. It's very rare to find someone from any group who seriously searches through all the major world belief systems and comes to a conclusion radically different than what is believed or at least considered acceptable thought anywhere near him. I've never seen anyone question Western though or scientific belief on the basis of "had I grown up in the far east I would see things differently. Maybe they really are right"
    – Schmerel
    Feb 13, 2023 at 18:35
  • @Schmerel I agree it is universal and rare; in what way is it circular? Also, just because of the rarity of such a truth-seeker, does that mean it is not correct? In particular, if someone is driven to "figure this out", should we discourage him?
    – Yehuda
    Feb 13, 2023 at 23:56

In the outset of the Kuzari, Rabbi Yehuda HaLevi (1075 – 1141) presents some rudimentary arguments of why one shouldn't accept some of the basic premises of Christianity and Islam vis a vis Judaism. Given that the foundation of Christianity and Islam are primarily based on 'revelation' to individual humans, which is hard to verify.

I imagine that given that Judaism predates Christianity and Islam, and given that our tradition claims an unbroken chain, it seems reasonable that Rishonim didn't tackle foundational elements of faith given basic stumbling blocks such as those outlined by the Kuzari. Nonetheless, there were various points in history where Judaism was challenged and Jewish scholars did have to outline arguments against the extent religions of the day. Pirkei Avot instructs us to "know what to respond to an apikoros" (Avot 2:14), perhaps for exactly this reason. In a sense, this mishna is endorsing the study of anything that would be required to respond to someone challenging Judaism.

Furthermore, over the years I have heard numerous discourses focusing on Deuteronomy 13 which instructs us not to harken to the words of "dreamers of dreams" i.e., false 'prophets'. The Torah itself, tells us this. In this regard, any person who instructs a Jew to go against the unbroken tradition as outlined in Tanach and chazal falls in this category. There are various commentaries which relate this perek directly to Jesus and Mohammed (I need to find the source again).

There were however, a number of Rishonim who, by necessity had to undergo public debates to defend the veracity of Judaism as challenged by various religious institutions present in that time and location. For example, the Disputation of Paris where the chief rabbi Yechiel of Paris defended Judaism in 1240, Disputation of Barcelona (year 1263, Ramban) and the Disputation of Tortosa (years 1413-1414, Hasdai Crescas, later than Rishonim...).

So although those Rishonim didn't, per se, endorse "comparative religious studies", they knew how to defend Judaism against their primarily Christian interlocutors.


In his Sefer Haikarim, R' Yosef Albo weighs in on this question:

We must call attention here to a question concerning religious belief. Is a person who professes a given religion permitted, or obliged, to investigate the principles of his religion in order to see whether they are true and in agreement with what we have laid down concerning the principles of divine law or not? And assuming that he is permitted to do this, has he the right to choose that religion which seems to him the truer or not? Whichever alternative we adopt offers great difficulties. In the first place, if we say that one professing a religion is obliged to investigate the principles of his religion, or is permitted to institute a comparison between the principles of his religion and those of another, the result will be that no religionist will be firm in his belief, and will therefore deserve no reward for belief, if he is not firm therein and free from doubt. For we can not call a thing belief except when the mind can not conceive the thing being otherwise, as we explained before. But if he investigates, he shows thereby that he is in doubt. And if we grant that he is permitted to investigate, suppose he has investigated and compared the principles of his religion with those of another, and found the principles of the other religion truer than those of his own, is he permitted to exchange his religion for the other? If he is permitted, the result will be that no man professing a religion can be made happy or be saved by his belief. For if, having compared the principles of his religion with those of the other and found the latter truer than his own, he has exchanged his religion for the other, it is still impossible for him to be firm in the belief of the other religion which he has chosen, because it is possible that after another investigation and a comparison between the second religion and a third, he may find the principles of the latter more satisfactory, and will have to change the second for the third, and in the same way the third for the fourth and the fourth for the fifth, and so on indefinitely. The result will be that no man will be firm in his belief until he has completed his investigation of all the religions in the world and chosen one in preference to all the rest. But there is the possibility that there is a religion at the extreme end of the inhabited world which is unknown to him, and which is truer than all the rest. No man therefore can be saved by his belief. For he can not have perfect faith until he has investigated all religions, and he can not investigate all religions, as we have seen. It would seem then that a person should not be allowed to investigate the principles of his religion so as to reach sure belief. But if our conclusion is that one is not allowed to investigate the principles of his religion, then one of two things must be true. Either all religions lead to human happiness, and one has no advantage over the other in the matter of reward and punishment, since no one is allowed to investigate the principles of his religion nor to change it for another. But it is quite impossible that religions which are directly opposed, the one affirming what the other denies, the one trinitarian, the other monotheistic, should equally lead to happiness. On the other hand, if we say that they do not both lead to happiness, but one of them only, a great absurdity will follow, namely that God is guilty of injustice (Heaven forbid!) in punishing those who profess a false religion, claiming to be divine, since the believer has no right to budge from his religion, or to change it for another, or to entertain any doubt concerning it. This difficulty applies to all divine religions and we must try to solve it. Our solution of this question is as follows: If it were true that all the known religions of the world are opposed to one another, every one saying that the other is not divine, the question we raised would be a difficult one indeed and hard to solve. But since all religions agree in accepting the divinity of one of them, the only objection to it being that, according to them, it was temporary in character and its time has passed, our opinion is that every one should investigate the principles of his religious belief. This applies without any doubt to those religions which are opposed to the one divine law, for no one should allow himself to be persuaded to believe something in opposition to the admittedly divine law, except after an investigation of the law, the second or the third, which he is inclined to believe, and the principles thereof, as we explained in the eighteenth chapter of this Book. As for the admittedly divine law, one who professes it should also inquire whether it is temporary or eternal; and if it should turn out not to be eternal, wherein the change is likely to occur. This is also Maimonides’ reason for saying in the fortieth chapter of the second book of the Guide of the Perplexed that it behooves every one to investigate the religion which he professes. He says there that the investigation should embrace two aspects. First, the religion itself. He must examine the commands and prohibitions, and if he finds that their sole purpose is to remove wrongdoing and violence and to maintain order in the affairs of the state, he must know that it is a conventional and not a divine law. If, on the other hand, he finds that in addition to removing wrongdoing and violence, it also takes care to inculcate true ideas about God and the angels, and endeavors to enlighten mankind and to awaken them to the nature of truth in relation to all things, that shows it is divine. The second aspect of investigation is that of the founder of the law in question. The alleged prophet or messenger who claims that the law is transmitted through him by God must be examined with a view to determine whether his claim is genuine or whether the contents of his law are borrowed from some one else. The thing to examine is the man’s character and conduct. The best test of genuineness is that he abstains from corporeal indulgences and holds them in contempt, especially the sense of touch, which is a disgrace to us, as Aristotle said. This is the gist of Maimonides’ words in that chapter. When he says that a test of the law itself is, if it takes pains to inculcate true ideas about God, etc., he is alluding to that religion which ascribes to God corporeality and trinity. And when he speaks of testing the moral qualities of the founder of the religion, he is alluding to that man who claimed that he was a prophet of the Arabs. According to Arab accounts he was addicted to physical and sexual indulgence. But this is not sufficient to enable us to differentiate a law laid down by a wise man, containing true principles such as a divine law might have, the founder himself being a man of noble character and conduct, from a divine law. There is no way of telling whether it is really a divine law or a human law which resembles a divine. My opinion therefore is that the two-fold examination of which Maimonides speaks is to be understood in the following way. First, the principles of the religion in question must be examined, to see whether they agree with the principles of divine law which we have mentioned. Also the secondary principles derived from the first must be examined, as we explained in the fifteenth chapter of this Book. If we find that the religion in question is in agreement with, or at least not in opposition to, the primary and secondary principles, and at the same time it endeavors to suppress wrongdoing and to inculcate true ideas among the people instead of the foolish fancies in vogue among women and common people, and to arouse them to a desire for human perfection, that shows it is divine. Similarly our Rabbis say in Torat Kohanim: Rabbi Akiba said, Thou shalt love thy neighbour as thyself is a great principle of the Torah. Ben Azzai said, This is the book of the generations of Adam is a greater principle of the Torah than that. By this is meant to indicate that a divine law must embrace both topics, the suppression of wrongdoing and violence among the inhabitants of the land, as alluded to in the expression, Thou shalt love thy neighbour as thyself, and the directing of the attention of the people to true ideas and to human perfection, which is alluded to in the verse beginning, This is the book of the generations of Adam, which continues with the words, In the day that God created man, in the likeness of God made He him, indicating that man has a human form which is in the likeness of God. And therefore he must be careful not to disgrace it, either in his own person or in the person of his neighbor, and he must see to it that it should survive death and unite with the celestial beings in the place from which it originally came. All this a divine law should contain. But it is still possible that it is the work of a wise man or wise men. We must therefore examine it from another aspect, namely the manner in which the messenger proved his authenticity, as one sent by God to transmit a law. If this matter is proved in a direct manner, as we explained in the eighteenth chapter of this book, the law is divine; if not, it is spurious and merely pretends to be divine, even though it acknowledges all principles, primary and derived, much more so if it opposes them or any one of them.

I am not quite sure what his answer is.

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