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.

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Further Reading: 

• 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).

Peter Adamson's picture

Sound quality

Apologies for the sound quality on this one which is not great - it was recorded over Skype.

Maciek Zajac's picture

Still I think it was a pretty good one

Episodes on Crescas were definitely most intresting among the Jewish philosophy ones.

If I may have a question on a much earlier topic - what Greek expression would Plato use to render the meaning of "moral/ethical knowledge"? Would Aristotle use a different expression? One of my friends remembers that in the metaphor of the cave Plato discerns four levels of knowledge the escaping philosopher reaches, each time using a different word. Would the appropriate expression be phronesis? Epsiteme with an adjective? Or something different still?

Peter Adamson's picture

Moral knowledge

Glad you liked Crescas. I kind of knew about him before writing the episodes so to me the big revelation was actually Ibn Paquda, whom I'd never read before.

Re. your terminology question I think (though maybe there is a passage I am not thinking of in Plato) that phronesis is defined as a specifically practical faculty first in Aristotle. In the passages where Socrates proposes an identity between virtue and knowledge he just calls virtue an episteme. It's right that Plato gives four kinds of cognition in the divided line, the top ones being noesis (all the way at the top) and then dianoia, which the Neoplatonists understood to mean respectively pure intellection and discursive thought. Neither of these seems to refer exclusively to theoretical or practical wisdom; indeed it would probably be fair to say that Aristotle's distinction between those two goes against the spirit of Plato's epistemology, which tends to see practical wisdom as intimately related to "theoretical" knowledge (i.e. grasp of the Forms).

Maciek Zajac's picture

Thanks a lot

That was very helpful :)

Tom Roche's picture

Crescas and Augustine

Correct me where wrong, but ...

In episode 166, Rudavsky says, and you concur, that "of course" Crescas didn't know Augustine. But

* before that (IIRC) she maintains, and you concur, that both Crescas and Gersonides were engaged with the Scholastic tradition
* the Scholastics (e.g. Aquinas) are seriously into Augustine
* Augustine is one of the more Jew-friendly Church Fathers (granted, not stiff competition :-)
* Crescas is born ... what ... 900 years after Augustine dies?

Sooo ... why "of course"? Am I missing something? And, speaking of missing something: given

* Rudavsky's @ OSU
* you're from NJ
* your demonstrated inability to resist comic opportunities however minor

I am shocked (shocked!) that you did not sign off episode 166 with, "goodbye, Columbus" :-)

Peter Adamson's picture


Oh, that's a very good point. I guess we would have to sort out whether it is likely he could have read the Confessions, which is rather a different proposition than, say, chatting with Ockham. But at least indirect influence could definitely be there if he is exposed to scholasticism.

Sorry to miss the joke opportunity; I won't let it happen again. By the way I'm from Boston, not NJ!

Dave Martin's picture

Time... And Time Again

Dear Peter,
Thanks for another excellent episode. I find it fascinating how the history keeps coming back to this problem of 'what is time'?

One thing struck me during this most recent episode: If time were not eternal, there must be difference between time and the units applicable to defining the extent of eternity. In our current reality, we are presumably experiencing the combined effects of both time and whatever medium contains eternity, but what was it like when only this eternity-filled medium existed (ie pre-time). Although this episode suggested several definitions of how 'time' exists and/or is perceived within a larger eternity, it's not evident that any of these philosophers adequately describe what there is when we have the medium for eternity to 'be' but no time to mark it out.

For example, with existence in such a timeless state, can anything change and can there be causality? It seems to me that for something to change, it not only has to have two states that are different, but also some separation between those states (usually that separation is 'time' for us). Without separation, the states simply coexist, and if they coexist, they are one and there is no possibility of change. For example, if I have a blue doorknob and then at some later time paint it red, there is change, but if I try to make it red and blue at the same time, it will always be unchangingly purple.

The nature of causality would have a similar problem, because causality requires change.

If causality breaks down in an existence in which time is not eternal, then a lot of other things would fall apart. For example, going back a good few episodes, Avicenna's proof of a necessary existent also breaks down, since it relies on axioms about the nature of causality to prove that a non- contingent existent must exist. In fact, if the nature of causality is not eternal, any pre-time creation cannot be ascribed to an agent, and we cannot know whether creation of the first contingent things actually needed an agent or not.

Further, if change is impossible without time, then time ( along with anything else) cannot be created, so it would seem that it must therefore be eternal.

Regards, Dave M

Peter Adamson's picture

Time, eternity and causation

Right, there is a whole cluster of problems here, and one big one as you mention is that it is not so obvious how A can be the caus of B without any temporal relations (at a minimum you might think B has to first not exist, then exist, in order to be caused). I think that Avicenna pretty much solves this with the essence existence distinction: if the essence is contingent whatever makes it exist is its cause and that can happen either eternally or with a temporal beginning. But people like al-Kindi would not agree: he makes "created" and "eternal" mutually exclusive.

And then another issue you raise here is what to say about the "time" before time would exist. This isn't necessarily absurd: you can have two types of time, one which is eternally elapsing, the other tied to the phenomena that are occurring once, say, the universe is created. This is Razi's view, and one that Crescas at least entertains. We'll find it again soon in Abu l-Barakat al-Baghdadi. However the usual move would be to say that God is in timeless eternity and that time simply begins when he wants it to, so there is no "temporal" extension prior to God's creative act.

Dave Martin's picture

Time, Eternity and all that

Hi Peter,
Thanks for your response. There's a few things here for me to think about.

I see the Avicenna solution to causality, but I'm not sure it's truly satisfying. The only 'causality' we ever experience is marked by a temporal extension. Even when you take something like, say, gravity that seems to be there all the time and holds planets in orbit, it can be seen to be causal because of the temporal changes caused on the motion of the planet. It's not clear to me that an 'eternal causality' (something that perpetually holds some other thing in existence) is the same phenomenon or that it would follow the same rules as causality we experience in a temporal reality. For example, how do we know that contingent things needed a 'cause' before the existence of time (in our temporal reality, they only need a cause to flip them from nonexistent to existent; in the pre-temporal reality, there can be no flipping, so do things that exist before time need a cause)? Indeed, how are the caused things differentiated from the things causing them in a motionless timeless reality?

I accept what you say about the possibility of two types of time, but - if there are indeed two types - we live in a reality where both types are elapsing. It's not clear that any of the axioms or logic we are using to do 'philosophy' would hold in that part of reality in which only one of the two were operating. (Another way of looking at this is to say that if there are two types of time, there must be two types of causality and we shouldn't asume we know how the second type works, or - in Avicenna's case- use it to prove the existence of God.)

Peter Adamson's picture

More on time

Yes, I agree both those points are a worry. With regard to the first what we need to do is make a case that causal dependence is possible without temporal sequence. Actually Avicenna's theory can be taken to mean that a cause is ALWAYS simultaneous with its effect: the cause is responsible for the effect's continued existence for as long as it goes on. On that view temporal sequence has nothing to do with causation at all! But that isn't an argument, only a way of looking at things that may not convince you. Gazali mentions an example that was offered by "the philosophers" of a finger eternally stirring water: no one would be confused about which is cause and which effect. Augustine gives a nice similar example of a foot eternally making a footprint in sand. What we need in any case is the idea of asymmetry without the idea of literal precedence.

Regarding the second point, you are right that there's an epistemic puzzle here: how do we know about this other kind of time which idein dependent of things we experience? Razi and Baghdadi both anticipate this and claim that time is immediately intelligible to us without needing motion as a prompt. This is something in the direction of the Kantian idea that time is just a condition of our experience rather than something we extract from experience. More on this in the episode on Baghdadi.

Dave Martin's picture

More on time

Thanks Peter
I'll look forward to the episode on Baghdadi.

I can't agree with Gazali and Augustine though. There is no way of knowing if the finger is moving the water or vice versa without applying knowledge gained from previous experiment. Similarly, you couldn't know whether the foot is making the impression or whether the formation of the impression was lowering the foot, without some preexisting knowledge about the nature of gravity. Therefore the idea of having 'no doubt' when doing either action 'eternally' is moot.

By the way, I don't think modern Physics has a comprehensive idea about what time is either, other than its passage seems to be associated with the direction of increasing chaos in the universe.