166 - Tamar Rudavsky on Gersonides and Crescas

Tamar Rudavsky joins Peter to talk about the two great medieval Jewish thinkers after Maimonides: Gersonides and Crescas.

• T. Rudavsky, “The Theory of Time in Maimonides and Crescas,” Viator 11 (1980), 289-320.

• T. Rudavsky (ed.), Divine Omniscience and Omnipotence in Medieval Philosophy, (Dordrecht: 1985).

• T. Rudavsky, Time Matters: Time, Creation and Cosmology in Medieval Jewish Philosophy, (Albany: 2000).

• T. Rudavsky and S. Nadler (eds), The Cambridge History of Jewish Philosophy: From Antiquity to the Seventeenth Century (Cambridge: 2009).

• T. Rudavsky, “Christian Scholasticism and Jewish Philosophy in the Fourteenth and Fifteenth Centuries," in D.H. Frank and O. Leaman (eds), The Cambridge Companion to Medieval Jewish Thought (Cambridge: 2003).

• T. Rudavsky, Jewish Philosophy in the Middle Ages: Science, Rationalism, and Religion (Oxford: 2018).

Note: this transcription was produced by automatic voice recognition software. It has been corrected by hand, but may still contain errors. We are very grateful to Tim Wittenborg for his production of the automated transcripts and for the efforts of a team of volunteer listeners who corrected the texts.

Peter Adamson: First, could you just provide the listeners with a quick reminder of who Gersonides and Crescas were? So their death dates are: Gersonides died in 1344, Crescas in 1410. So that means they weren't contemporaries, they didn't know each other, but they're often discussed together. So can you just sort of say who they are and maybe give us an idea of why people tend to group them together in that way?

Tamar Rudavsky: Well, I think we can start with why they are grouped together. That's a pretty straightforward answer. We can think of Jewish philosophy as being pre-Maimonides and post-Maimonides, and both Gersonides and Crescas are responding to Maimonides' Guide for the Perplexed. They respond in different ways, but they're both seen as taking on issues in Maimonides' Guide. Gersonides was born in France, 1288. He was extremely influential as a mathematician, astronomer, and philosopher. His major work, the Milhamoth Hashem, or Milhamoth Adonai, The Wars of the Lord, was written in response to Maimonides' Guide for the Perplexed. Crescas wrote somewhat later, 1413-1440, in Barcelona. His major work, Sefer or Adonai, the Book of the Light of the Lord, was finished several months before his death, and it was written as a polemic against both Maimonides and Gersonides. So if we see the trajectory from Maimonides' onward, we see Gersonides taking on some of Maimonides' positions, but not all, and Gersonides taking on both.

Peter Adamson: Not only do these two philosophers get associated with each other as different reactions to Maimonides, but I think they're often seen - at least by people who don't know their works very well - as conveniently opposed figures. So Gersonides is a rationalist, he's a commentator on Averroes, and Crescas is an anti-rationalist because he's famous for this attack on Aristotelian natural philosophy. And to be honest, this is pretty much what I thought before I started looking into them more to write about them for the podcasts. But actually reading them more carefully, I was struck by the fact that - as I mentioned at the end of the last episode - their works are very similar to each other. So they both have this habit of presenting other philosophers' arguments in great detail, and they'll go through all the premises and so on, and then they'll refute the arguments or say what's wrong with the arguments. So do you think that the two of them actually have more in common than people often are aware of?

Tamar Rudavsky: Well, that's an interesting question - yes and no. So they do share certain similarities, but yet I think their objectives are very different. In terms of similarities, both are writing under the shadow of Christian scholasticism. Both are aware of scholastic method. Scholasticism is becoming more and more popular in the Jewish idiom, and so we find Jewish philosophers really writing in a much more rigorous, what we would call, analytic style. They're aping Aristotle, they're aping the scholastics. I mean, not aping, but they're really copying methodologically and pedagogically the sort of rigor that we don't find, for example, if we read Maimonides' Guide for the Perplexed. I think students are often really surprised to find almost a lack of rigorous philosophical argument in Maimonides' Guide. Gersonides says at the outset that he wants to render philosophy scientific. He's very concerned with the rational aspect of philosophy, and we find Crescas in that same camp. So yes, they do share certain methodological similarities, but I would then go on to argue that they're really very different in terms of what they see their role to be. Crescas is much more global than Gersonides, and he really takes on a global attack upon the very doing of philosophy. He's directing his work against all Aristotelians, Maimonides, Gersonides, anyone who uses Aristotle's arguments to undermine Judaism. And so he really sees Aristotle's physics and metaphysics as threatening the fabric of Judaism, and he is determined to marshal whatever he needs to dismantle Aristotle.

Peter Adamson: And that's clearly not Gersonides' point of view.

Tamar Rudavsky: No, absolutely not. I would say that Gersonides is quite comfortable with philosophy. He's a philosopher's philosopher, and perhaps that's why I've always been attracted to him. He's much more concerned to render Jewish beliefs even more rational than anyone else had done. I mean, he's very much within the rationalist camp. He really takes on philosophical arguments in support of Judaism. He doesn't see the philosophical arguments as threatening Judaism in any way.

Peter Adamson: Could I just follow up on something you said there, which is that both of them are writing in the shadow of Latin scholasticism, which of course is something I haven't covered in the podcast yet. But nonetheless, I think it might be worth saying something about how much they knew about Latin scholastic philosophers. So we're talking about Gersonides living in the first half of the 14th century, Crescas in the second half of the 14th century. I mean, he died in 1410, so already into the 15th century. So that means in theory, they could have been aware of authors like Aquinas or even Scotus. How plausible is it to think that they were actually reading the works of the famous scholastic philosophers? I know there is a controversy about whether Gersonides read anything in Latin, for example.

Tamar Rudavsky: I wish I could give a definitive answer. There is quite a lot of disagreement over the extent to which Gersonides was aware of Latin writers and whether or not he used Latin or was aware of Latin texts. I personally feel that he did make use of works written in Latin. I think there's good evidence for that. I think it's also worth noting that he himself worked in Avignon at the papal court, the very two years that Ockham was there. And if you look at Ockham's theory, for example, of future contingents, and you compare it to Gersonides' theory of future contingents, both of them are espousing a minority view which had not been developed before in either Jewish or scholastic philosophy. So to me, it's remarkably naive to claim that Gersonides is writing in a vacuum. He's at the court. He's doing astronomy. He's the papal astronomer. He's having works commissioned. In Crescas's case also, he's writing during the height of the scholastic world. There are a lot of similarities between him and Nicole Oresme, between him and Peter Auriol. Zev Harvey has written extensively on the similarities. Again, we don't have definitive proof, but the writings suggest that Crescas was very much aware of what was happening in the 14th century among scholastics.

Peter Adamson: That's really interesting. I guess when they invent a time machine, the first thing we should do is go back and listen to Gersonides arguing with Ockham about future contingents.

Tamar Rudavsky: Oh, absolutely. And I'm convinced that they probably spoke in ProvenÁal, because we know that Gersonides knew ProvenÁal, Ockham knew ProvenÁal. What are they talking as they're circling around the court on a Tuesday afternoon?

Peter Adamson: Okay, note to self, before they invent time travel, learn ProvenÁal so that I can listen to them. Right. Okay, so I wanted to focus in particular on one philosophical topic, because obviously both Crescas and Gersonides talk about many philosophical topics, and we can't cover all that. So I thought maybe we could focus on one that you've written about a lot, which is time and eternity. And beginning with Gersonides, he seems to have a very unusual view on this, because he denies the eternity of the universe, as I understand it. But on the other hand, he thinks that time is eternal. So time has been, as it were, there the whole time that God has been there. Maybe that would be one way of thinking about it. But the physical universe has come into existence at some particular moment, so a finite number of years ago. So first of all, I guess, is that right? And second of all, how does he defend that view?

Tamar Rudavsky: He actually has a fairly, as you suggest, he has a fairly complex view. And his longest book in Wars of the Lord is devoted to the problem of creation. Book six is actually longer than the other five books together. Well, I'm not counting book five, which is his book on astronomy, but books one through four. And he's responding in part to Maimonides. Now, it's interesting, because I imagine that when you presented Maimonides, you talked to great length about how ambiguous Maimonides himself is with respect to the doctrine of creation. Maimonides can be read as postulating creation ex nihilo. He can be read as an eternal creation theorist. He can be read as an epistemological skeptic. I mean, there are many ways of unpacking what Maimonides has in mind. And so Maimonides' own theory is ambiguous. Gersonides takes on Maimonides, positions Maimonides as an ex nihilo theorist. So he reads Maimonides' Guide very straightforwardly and takes on Maimonides' theories of time and creation. And so what he will want to argue is that, as you suggested, the world itself is eternal in the sense that it's engendered out of what he calls a pre-existent matter. He distinguishes two types of matter, Geshem and Homer, taken from the book of Genesis, he's not being particularly creative on this score. But he does argue that the world was created out of an eternally pre-existent matter. And yet, at the same time, he wants to argue time is finite. And so the world itself, the temporal sphere, is not eternal but was actually generated. And he makes a very interesting point, arguing that with respect to potentiality, the past itself is finite and contains no potency. Only the future contains potency. So he's really distinguishing himself from the Aristotelian model of time. And I find that very interesting because it then allows him, in his material having to do with future contingents, to claim that the future is open once he's allowed for the potency embedded in the future rather than the past.

Peter Adamson: So let me get clear on something there. So there's pre-existing matter before the universe as we know and love it exists. And you said that the past is finite and that the temporal sphere came into existence at a certain moment, a finite number of years ago. Does he actually think that time itself came into existence when the physical universe came into existence? Or does he think that time extends backwards into the period when there was only pre-existing matter?

Tamar Rudavsky: I read him in the latter way that time and motion are finite but ungenerated. So it's an odd combination. So Homer itself has an underlying temporal thread to it.

Peter Adamson: So it's sort of like maybe he thinks something like organized time or time that's measured comes into existence when the cosmos starts to move.

Tamar Rudavsky: Right. So he doesn't make the sort of arguments that Plato, for example, makes in the Timaeus.

Peter Adamson: Actually, you just mentioned Plato, and Plato is always mentioned in the context of these eternity debates in the Arabic speaking world as someone who did in fact believe that there was pre-existing matter and then the cosmos came to be because the demiurge comes along and organizes the matter. But I know that also in the rabbinical tradition, there was this tradition of rabbis talking on the basis of Genesis about a pre-existing material substrate. So do you think that Gersonides would have seen himself as a follower of Plato or the rabbinical literature or both? I mean, did he think there was a kind of nice confluence between, say, the Mishnah and Plato on this issue?

Tamar Rudavsky: Oh, he definitely uses both. I mean, he sees himself in book six as bringing together both the rabbinic strand and the philosophical strand. He uses both, as you rightly point out, that there's a long rabbinical tradition of reading the first verses in Genesis as supporting, well, not so much an eternity model, but an eternal matter, a pre-existing matter. And God still plays a role in that Genesis model. And so I think this is the sort of model that Gersonides has in mind.

Peter Adamson: Another question, I guess, that arises here is, does he have a convincing argument for this? So I mean, it's one thing to say, 'oh, look, I agree with Plato. I agree with the rabbis, the ancient rabbis, so I must be right.' But presumably he has more to offer here than kind of appeal to authority. So is his main idea going to be actually, in a way, an Aristotelian one, which is that if you don't have some kind of potential, in other words, matter, that can be actualized when God creates the universe, then there's nothing for God to work with. And so there's no way he could actually create?

Tamar Rudavsky: No, he actually, it's very interesting. In book six, he provides us with about a dozen very carefully worked out arguments having to do with the finite divisibility of time. So he really takes on the whole theory of the continuum, infinite divisibility, and why it is that an infinite sequence can't be infinitely divided. He's very much aware of the Aristotelian arguments as they come in through the physics. I mean, we've got the super commentaries as well. And so no, no, he's not at all working on the basis. In fact, in book six, I mean, I should point out he doesn't quote rabbinic authorities at all - very much unlike Maimonides. If you read the Guide, Maimonides is quoting right and left, but Gersonides rarely quotes scripture in support of a philosophical position. And so what we have is sustained analytic argument. That probably, I think I would say the first example of sustained analytic argument in Jewish philosophy.

Peter Adamson: So that's interesting because that, in a way, reinforces this contrast we were talking about before between Gersonides, who's this kind of hard-nosed philosopher who really wants to argue within the philosophical tradition, and Crescas, who, of course, is much more like a critic of the philosophical tradition, even though they both write text full of arguments. And Crescas actually is also quite well known for having interesting things to say about time. So in this case, what he does is much more of a wholesale criticism of the Aristotelian conception of time. So what does he not like about Aristotle's conception of time? And what conception of time does he want to replace it with?

Tamar Rudavsky: Well, Crescas, as I said earlier, is trying to weaken Aristotle's hold on Jewish philosophy. And he sees that hold as really cemented in the 26 propositions that Maimonides lays out in the Guide for the Perplexed. These propositions form the basis of Maimonides' metaphysics. They're primarily Aristotelian. They're written in part in response to Islamic Kalam ontology. And Maimonides is replacing the Kalam with these 26 propositions. But Crescas turns to those propositions and dismantles them one by one. The ones that are obviously most germane today have to do with time and space. And so what Crescas will want to do is claim that it's these propositions that lead philosophers to reject creation. And so what he tries to do is reject, well, he starts first by rejecting Aristotle's theory of time, replacing it with what some scholars have called a subjective conception of time, suggesting that time is defined in terms of what he calls the duration of the life of the thinking soul. So this is quite different from anything that you'll find in Jewish philosophy. It actually reminds me of Augustine's subjective conception of time.

Peter Adamson: I was just going to say that.

Tamar Rudavsky: Yeah. Oh, very, very much. Very, very much. Now, obviously, Crescas hasn't read Augustine, but thinking about theories of time, there are only so many ways one can characterize time. And you're rejecting wholesale the Aristotelian conception. There are just only so many moves you can make. And so what he wants to claim is that the existence of time is only in the human soul. It's only because we have a mental conception of measurement that time even exists. Time becomes definite only by being measured by motion. And so here he's certainly adhering to certain Aristotelian pieces, but replacing the objective measure with a subjective awareness of time.

Peter Adamson: Actually, I'm always fascinated by this kind of subjective theory of time. And it always makes me wonder the same thing, both in Augustine and in Crescas, and whoever else says it. Because it seems clear that they're saying, 'well, there's no time out in the world.' So it's going on, as it were, in our minds. But then it seems to me like that could be understood in two different ways. One way would be to say, 'well, look, our own mental life is conditioned by time, really.' And so when we experience our thoughts or our memories kind of going on from moment to moment, that experience is conditioned by this phenomenon, which is time. So I would almost say it's real, but it's a mental phenomenon rather than objective phenomenon. So that's one way to understand it. And another way to understand it would be that time is basically an illusion. So we project our experience of things as being temporal onto the world, but actually it's kind of an artifact of just the way we think. And there isn't anything either inside the mind or outside the mind that's genuinely temporal. I'm not sure that that distinction makes sense. But if it does, which side of that do you think that Crescas would be on?

Tamar Rudavsky: I think it does make sense. Now, I'll lay my cards on the table. I think Augustine adopts the second, and I also think that Crescas adopts the second. So I'm reading the subjectivity of time in a fairly radical way. I mean, I think they really - well, let's stick with Crescas. I mean, I think Crescas really wants to say that time is nothing but duration. Milhamoth Hashem is the Hebrew term that he uses. Time is not identified with anything outside the soul, with physical motion, with bodies, with temporal flux, et cetera, et cetera. So I think this is fairly radical.

Peter Adamson: And it's also not identified with the objective fact that our thoughts are somehow elapsing. It's really like a mentally produced phenomenon. That's amazing, right? I mean, it almost inevitably bears comparison with Kant as well. So actually, this is another thing we should do if we get a time machine. We should collect Kant, Crescas, and Augustine and make them all talk to each other about time. So speaking of the future and what happened after Crescas, let's not go as far as Kant, but let's go a little bit into the legacy of both Gersonides and Crescas. So I guess with Gersonides, when I think about his later influence, I think about him mostly in terms of his super commentaries on Averroes rather than in terms of the Wars of the Lord. And so I would think of him as a kind of forerunner of Jewish Averroism in the Renaissance, which is something I guess I'll cover eventually. With Crescas, the thing that leaps to mind is that he has some role to play in maybe helping to kickstart the rise of modern science because of his criticisms of Aristotelian natural philosophy. But these are kind of vague ideas. So could you say something a little bit more about what kind of influence both of them exerted in the later tradition?

Tamar Rudavsky: Sure. Certainly, certainly Gersonides' super-commentaries on Averroes were tremendously influential. But I want to suggest that the Wars of the Lord was as well. Interestingly, the book was reviled by his immediate successors. The title, Milhamoth Hashem, was transposed to be Milhamoth Neget Hashem, Wars Against the Lord. And so most of his successors really found Gersonides just quite difficult. I mean, he was just far to the, what, I don't know if you say to the right or to the left, but he was far more extreme in his ultra-rationalism than most philosophers. Interestingly, he was rediscovered in the 19th century by modern Jewish philosophers looking for rationalist models in the medieval period. And so you look at the early 19th century German Jewish reformers, Maimonides wasn't even rationalist enough for them, and so Gersonides becomes their role model. And so he really enjoys a renaissance in the 19th and 20th century. And I think that's one reason perhaps why he's been so popular in the latter half of the 20th century. Because of his rigor - he's a logician as well. We didn't even talk about his logical work, but he writes a work in logic. In his astronomy, I must take the opportunity to say that he's one of two Jewish philosophers who have lunar craters named after them.

Peter Adamson: Who is the other one. Is it you?

Tamar Rudavsky: Abraham Ibn Ezra, writing a hundred years earlier from Jewish philosopher and astrologer. And I'm guessing the reason they have craters is because both of them were so interested in astronomy and astrology. So we have the legacy in astronomy, the legacy in astrology, and of course we haven't had time to say anything about his astrology. And his proto and extreme rationalism, and he says in, and I want to just read a sentence from the Wars, "if the literal sense of the Torah, of scripture, differs from reason, it is necessary to interpret those passages in accordance with the demands of reason." This is really a remarkable statement for a Jewish philosopher to be making in the early 14th century. Maimonides danced around that issue, but Gersonides says very, very clearly that reason is not incompatible with the true understanding of Torah.

Peter Adamson: Yeah, he clearly learned a lot from reading Averroes, right?

Tamar Rudavsky: That is exactly right. And so I really see him as a champion for religious rationalism.

Peter Adamson: And so is Crescas basically a hero of the other side, so the people who thought that even Maimonides was already going too far in the rationalist direction would presumably have quite welcomed Crescas' attack.

Tamar Rudavsky: Exactly. So Crescas becomes more a spokesperson for - I don't want to say for apologetics, because that's really not taking him fully seriously. I mean, he's a very serious philosopher, but he does reinstate the balance, and he really does see himself as a protector of the faith. And he has been seen that way, of course, by his successors. But I think Zev Harvey made a wonderful point. I mean, he suggested that it's the critique of Aristotelian science undertaken by Crescas that really opens the possibility for the dismantling of Aristotelian science. And so one might argue that Crescas' critique of Aristotle helped lay the groundwork for the abandonment of Aristotelian science in subsequent centuries. So we have already, you know, in the 15th, 16th, 17th century - even in Spinoza we see reference back to Crescas. Crescas allows for alternative scientific worldviews. So in a way he's a forerunner. I mean, maybe I'm exaggerating a little, but a forerunner of the scientific revolution.

Peter Adamson: Right, because sometimes the most scientific thing you can do is point out the mistakes of earlier scientists. I think another, just maybe a last thought that I would have about this is that Maimonides himself, of course, in some of his moods, he's very keen to emphasize the limits of reason, the things that we can't know, say about the heavenly spheres. And so you could think of Gersonides and Crescas not as a kind of fan and critic of Maimonides, but as people who are latching onto different moments in this very complicated philosophical profile of Maimonides. So Gersonides running with the rationalist elements and Crescas running with more skeptical elements.

Tamar Rudavsky: Right. Although Gersonides is very clear there are very few limits to human intellect. And I'm guessing, if you think about the difference between Maimonides and Gersonides, Maimonides says very clearly in the Guide: I've done my best to learn astronomy. I've studied al-Bitruji. I've studied the eccentric and the epicycle - maybe someone more intelligent than I can figure out these details. Then Gersonides comes along, one of the most brilliant astronomers of the period. And so therein lies the difference.