210. John Marenbon on Peter Abelard

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John Marenbon returns to the podcast to discuss Abelard's views on necessity and freedom.



Further Reading

• J. Marenbon, Early medieval philosophy (480-1150): an Introduction (London, 1983).

• J. Marenbon, "Abelard’s Concept of Possibility" in B. Mojsisch and O. Puta (eds) Historia Philosophiae Medii Aevi. Studien zur Geschichte der Philosophie des Mittelalters (Amsterdam: 1991), 595-609.

• J. Marenbon, The Philosophy of Peter Abelard (Cambridge: 1997).

J. Marenbon, Aristotelian Logic, Platonism, and the Context of Early Medieval Philosophy in the West (Aldershot, 2000).

• J. Marenbon, Abelard in Four Dimensions (Notre Dame: 2013).


T. Franke on 8 February 2015

Abaelard, possibility and freedom: What for?

I thought about Plato and possibility, applied to the future. There is at least one example: Socrates in the Apology, talking about his own future after death. As something unknown to him it is a classical situation of *mythos*. Plato's solution is just arguing for all future possibilities ... and god and god's knowledge is not of major importance. For Plato, human beings are in an eternal cycle of rebirths, with no end of history and no final judgement. The future is not of the same importance, then. It seems to me that Abaelard's and other medieval thinkers' problem is created by the combination of philosophy with an unphilosophical religious belief in a special version of god which was treated as certain knowledge instead of being uncertain (and possibly doubtful) mythos. The question is, whether this has more value for philosophy itself than just being a student's exercise in thought. It surely is important for the history of ideas leading society into mental slavery or back to freedom. In this respect, Abaelard's uncomfortable thoughts may have had a positive influence.

In reply to by T. Franke

Kson on 8 February 2015

This is a pretty uncharitable

This is a pretty uncharitable view of Abelards solution to the sea battle argument. It's not really mentioned in the podcast but Abelard views the problem the exact same way a modern logician would, and then points out, as a modern logician would, that it's a case of the modal scope fallacy.
Wherby you cannot get from Necessarily, if A then B to if A, then necessarily B.
If some problem of future contingents actually remains once one has removed all errors in the modal reasoning is open to debate. Some belive problems do remain, some do not. Note for example http://www.iep.utm.edu/foreknow/#H5 by Norman Swartz. The jury might still be out, but I wouldn't find it suprising if Abelard actually got the whole thing right from the beginning, a thousand years ago.

In reply to by Kson

T. Franke on 9 February 2015

Aristotle and Abaelard

I do not see any philosophical tension in Aristotle's sea battle argument. It can easily be solved by an emphasis on precision in using language. Today is not tomorrow, and a possibility is not its realization. If admiral A will have won the battle, the possibility of admiral B to win the battle will have vanished. If A then necessarily not-B, in short words. The future is open. Whereas Abaelard's strong assumption of an omniscient god (where does he take this assumption from?) makes it really problematic, leading directly into the hell of determinism: Today *is* now tomorrow, it's a world without any possibilities.

In reply to by T. Franke

Kson on 9 February 2015

It's interesting that you say

It's interesting that you say this because it seems to be a natural reaction when presented with the argument, historical early "solutions" focused on tense, and Aristotle himself made it central in the very framing of necessity and contingency, while Abelard begins moving to a more atemporal treatment of necessity and contingency. Today when speaking of necessity and possibility and also truth it is generally a atemporal viewpoint that is taken and not the other way around.

In reply to by Kson

T. Franke on 10 February 2015

Further definition needed

The question is whether the problem is properly defined if the question of temporality is not part of the problem's definition, yet expected to be implicitly "clear". It has to be explained how such a thing like "possibility" has to be understood without time: A decided question naturally does not have any more the possibility to realize itself this way or that way. So, in addition to the definitional problem with time we have a definitional problem with "possibility". In this respect my example of Socrates talking about his future after death is not appropriate: He only does not know it (mythos), yet the question is decided already. We then have at least two kinds of "possibility": (a) Real possibility: A question is undecided. (b) Subjective possibility: The question is decided, yet you do not know the answer and have to *expect* various possibilities. Let us add a third definition: (c) Theoretical possibility: All "naturally" possible decisions for a question, regardless if it is decided or not, or whether you know about the decision or not. Still, the whole thing looks like playing with language. The modal scope fallacy seems to be less a fallacy due to an inappropriate use of logic than more a fallacy due to an under-determined problem presented in a language not spoken by most people. But where is the real philosophical problem? The only problem I can see is the problem of determinism in case of the omniscient god (and its consequences). But this is not a problem of logic, it is a result of logic applied to premises.

In reply to by T. Franke

T. Franke on 11 February 2015

Finally I have understood it

OK, finally even I managed to understand the Modal Scope Fallacy: It is simply, that from the necessity, that god's foreknowledge and future actions have to correspond, it does not follow, that the future actions are determined by god's foreknowledge. If any, it is rather the other way round: If I tomorrow decide (freely) to act otherwise, it is rather god who has to adjust his foreknowledge accordingly, so to say (or better said: an omniscient god orients his foreknowledge right from the beginning to the later freely altered decision).

What is missing is an explanation how it is possible that something is known in advance while the (free) decision for it is taken after this knowledge is there: This is then the real philosophical challenge. It is not clear whether it is possible. As the podcast tells, Abaelard failed here.

I had a real hard time yesterday evening browsing desperately for hours through dozens of Web pages providing various explanations for the Modal Scope Fallacy. I experienced, that each of these Web pages had its very own approach, partially presenting weird examples, and almost no Web page gave a really didactic explanation

One page tried to explain it with an omniscient mother who knows which studies I will choose after school ... hard to imagine a life with an omniscient mother, and even harder to imagine any freedom of choice under an omniscient mother ...

All these funny Web pages expected the reader to cheer up to the solution and to have no further questions (like: how it is possible that there is freedom if it is known in advance, see above). This Hurray atmosphere really made me suspicious: Why do they stop thinking exactly when it becomes interesting?

At midnight I gave up: I couldn't understand it, and so I made some angry notes about the diverse unsubstantiated and ridiculuous claims of the various Web pages ... and this was the moment when insight suddenly struck me: I just took playfully into consideration that the possibility in question is the "real possibility" (nobody explained that so far, nobody suggested that so far, and it is the least to expect) and there it was the solution! This unlcear definition of possibility is one of the key obstacles to understand what is meant with the Modal Scope Fallacy.

I listened to the podcast a second time, and this time I really enjoyed it :-)

In reply to by Kson

Peter Adamson on 9 February 2015


But didn't John Marenbon say precisely that, I mean, that Abelard got the scope fallacy point? I think the question is just whether that is good enough, especially if you also have the accidental necessity of the past (because if you add that, then you wind up with necessarily A, and if A implies B then that gives you necessarily B).

In reply to by Peter Adamson

Kson on 9 February 2015

"But didn't John Marenbon say

"But didn't John Marenbon say precisely that, I mean, that Abelard got the scope fallacy point? I think the question is just whether that is good enough."

I'm in total agreement with you here, and as I pointed out some modern philosophers think that this is indeed good enough.

"(because if you add that, then you wind up with necessarily A, and if A implies B then that gives you necessarily B)."

You would also need that A necessarily implies B, otherwise you would just get that B is true but not necessarily soo or to put it more formally:
□(A→B) → (□A→□B), where □ denotes necessity.

Here's the egg argument: If God knows that I will eat eggs tomorrow morning, it is necessary that I eat eggs tomorrow. Or to put it more formally:
□(GKA→A), GK□A therefore □A, where GK denotes "God knows", the error plainly seen is that the correct renditioning of God necessarily knows A is □GKA not GK□A wich means God knows that A is necessary. But if you substitute GK□A for □GKA you won't get the conclusion □A but just A. It's another case of the modal scope error.

To quote Torkel Franzen, logician-philosopher on this very topic:
"Indeed, posters like to ask whether, if God stands before them and tells them that they will eat a pizza tomorrow, they can still freely choose to eat a hot dog instead. The answer, logically impeccable, that they certainly can, but by assumption won't, naturally fails to satisfy."

In reply to by Kson

Peter Adamson on 10 February 2015

Necessary implication

Yes, good point - I was assuming that the if-then relation is a necessary one. Which, I think, is quite plausible in this case: if there is any inference from past truth to future event, then it is probably a necessary implication. I mean:

if: it is true at t1 that S is P at t2,
then: S is P at t2

Can we imagine someone thinking that the if-then relation is merely contingently true? (As opposed to thinking that the antecedent is contingently true.)

And then as we've agreed, the necessity of the past will give you the antecedent being not merely true but necessarily true, so the deterministic argument goes through.

In reply to by Peter Adamson

Kson on 12 February 2015

"if: it is true at t1 that S

"if: it is true at t1 that S is P at t2,
then: S is P at t2"

One reasonable solution to this is just to ban tense statements like " true at t1". But Abelard himself gave another perfectly reasonable solution to the above statement, namely that the proposition it expresses is first to be read as a future tense statement, then as a past tense statement, to give an example:
"If its true now that it will rain tomorrow, it will rain tomorrow" is to be read as "If it will rain tomorrow it's true now that it will rain tomorrow".

This reading solves a number of conceptual problems. First of all It does not invert the truth making relation, It makes sense to say: 'Snow is white' is true because snow is white, but not to say: snow is white because 'Snow is white' is true.
Secondly, it stops you from making any statement be about the past by just adding "it was true yesterday" at the beginning of the sentence, it seems unreasonable on the face of it to say that "it was true yesterday that 1+1=2" is a statement concerning the past when it's really a mathematical assertion masquerading as historical fact.

Wojciech on 8 February 2015

Abelard in Four Dimensions

Thanks for another great podcast. As for the damnandus issue, it's worth adding Prof. Marenbon's "Abelard in Four Dimensions" (University of Notre Dame Press, 2013) to the bibliography, esp. chapters 2 and 4.

Tim on 10 February 2015

There *May* Be a Sea-Battle Tomorrow

I was on a long drive through New Mexico today while listening to this episode when I passed a traffic sign warning me in large text that "Dust Storms May Exist." Maybe next episode, John and Peter can move on from determinism and God's omniscience to the necessary contingents of NMDOT signs.

In reply to by Tim

Peter Adamson on 10 February 2015

Dust storms may exist

So great! There is probably a whole genre of philosophical street signs, now that I come to think of it... sounds like a Twitter feed waiting to happen.

Was that a yolk? on 10 February 2015

Was that a yolk?

Did you say "ovo" instead of "although" at approximately 14:58?

In reply to by Was that a yolk?

Peter Adamson on 10 February 2015

Egg-stremely funny

Sadly no - for once I didn't mean the pun! Wish I'd thought of it though.

Thomas Mirus on 30 May 2015

When is someone going to say

When is someone going to say that God exists outside of time, and thus there is no issue of "foreknowledge" impacting our freedom? Since that is what I was taught in Catholic high school, it's interesting to see that it's not an insight which can be taken for granted; rather, it was hard-won from centuries of theological and philosophical debates.

In reply to by Thomas Mirus

Peter Adamson on 31 May 2015

Atemporal eternity

Well, I suppose a lot of people would credit this idea to Boethius; but perhaps it emerges clearly for the first time in 13th century scholasticism. So, coming up soon on the podcast.

In reply to by Peter Adamson

Alexander Johnson on 26 April 2019


Without the Christian background, I had the same thought.  If God exists outside time, then for him he knows i will eat eggs at t2.  When you add in free will, the path goes i eat eggs at t2, God knows at all t that i ate eggs at t2, therefore God knows at t1 that I eat eggs at t2.  This seems consistent with choice and "foreknowledge" because then causality isn't locked to the timeline.  This then implies that I already caused my entire timeline , beyond my experiencing the causation. 

One thing I always notice in these discussions (in general, not here), is that people get confused on the whole knowing the future thing.  Let's say I have a vision, and know that I will eat eggs tomorrow.  Now let's consider two timelines, timeline A in which I recieved this foreknowledge, and timeline B in which I did not recieve foreknowledge.  It seems to me that it would be a fallacy to believe that the foreknowledge would be of timeline B, that I had a vision of eating eggs in a timeline in which i did not know I was eating eggs as it wouldn't be foreknowledge, but rather alternate timeline knowledge.  Therefore, the foreknowledge would exist in timeline A, which then means that the thing I have foreknowledge of must already be compatable with the fact that I recieved the foreknowledge.  Also the very fact that we are discussing foreknowledge, implies that the timeline is already set, which then implies that "Everything that will happen has already happened in spacetime" 

or as Red Dwarf put it in episode 2:

LISTER: Hey, it hasn’t happened, has it? It has “will have going to have happened” happened, but it hasn’t actually “happened” happened yet, actually.

RIMMER: Poppycock! It will be happened; it shall be going to be happening; it will be was an event that could will have been taken place in the future. Simple as that.

In reply to by Alexander Johnson

Peter Adamson on 28 April 2019


Firstly, well done getting Red Dwarf onto the podcast website! Long overdue.

Secondly, I'm not sure I buy your solution, at least not entirely. I agree that by acting one can make it have always been the case that one would so act: thus by eating eggs today by free choice, I can make it true now that I am eating eggs but also this action could be the explanation for why it was already true yesterday that I would today eat eggs. I think the 14th century scholastics nailed this quite well. The part I don't buy in what you say is where we introduce foreknowledge: how can I both know that I will eat eggs tomorrow, while still being in a positio not to eat eggs if I decide not to? It seems obvious that I could simply choose, at the fateful hour, to do something other than what I "knew" (we should really say "believed") I would do. The problem here comes from introducing not just truths about the future - which can remain hidden from us - but knowledge about it. This shows that the problem of foreknowledge is not identical to the more general problem of sea battle style determinism, as is often supposed.

In reply to by Peter Adamson

Alexander Johnson on 7 May 2019

Subject Foreknowledge

First, let us consider the compatibility of free will with an non-active divine foreknowledge.  Let’s say there is a room being recorded.  At time t, one of the people in the room chooses eggs over bacon.  Now let’s say someone took that recording and time traveled to some moment before time t, and played it for me in an isolated room.  It would seem silly to suggest that the people had free will before, but no longer do now that someone in a small isolated room has seen it.  Therefore, it seems like free will should be compatible with divine foreknowledge, even at 100% certainty.

Now let’s consider the case of subject foreknowledge and free will.  Let’s say I have 100% certainty about the contingent actions of an individual, I also know what decisions I will make.  If a person is in a maze, and there are 2 paths, path A and path B.  Without action, the person freely decides between the two paths.  If I tell them they will take path A, and they are willing, they will do so, so that is uninteresting.  So, let’s consider the unwilling actor.  If I tell them they will take path A, they will take path B.  If I tell them they will take path B, they will take path A.  I also know what I am going to tell them (since I know my own actions).  So I still know what path they will take, and they still freely choose which path (even after I announce a side, they can still choose to take that side, even though I know they won’t).  So here, divine foreknowledge and free will are compatible, but subject foreknowledge is not.

Changing the scenario, path A and path B converge on point x.  I tell the subject they will arrive at x.  They think x is on path A, take path B, and end up at x anyways.  Here, divine and subject foreknowledge seem compatible, but free will not.

However, consider a 3rd scenario.  I tell the subject they will arrive at x.  X appears to lie on path A, however it does not.  X does lie on path B.  So I know the subject will freely choose to take path B to attempt to defy foreknowledge, only to reach x anyways.  Here, divine foreknowledge, subject foreknowledge, and free will all work together.

So this seems to imply that divine foreknowledge is compatible with free will, but that not all forms of subject foreknowledge are possible (aka, those by which you knowing it would cause it not to happen), and subject foreknowledge being possible is contingent on it happening with the contingent condition of me having the foreknowledge already accounted for.

-Alex "Otterlex" Johnson

PS:  this is one of my first attempts at a formal arguement for a philosophical position, i hope it is readable.

PPS:  @Emily, lol! that video is great.

In reply to by Alexander Johnson

Emily on 9 May 2019

Otterly Enjoyable

What if the subject (let's call her Coriander The Contrary Hen for argument's sake) by some metaphysical accident has foreknowledge of your plans and is aware that she is being observed, thus calling into play the Hawthorne effect.

Is it Coriander's behavior that's being manipulated or the philosopher's conclusions? Who, if any, of the participants has free will? In the words of the late, great Aretha Franklin, who's zoomin' who?!

PS - @Otterlex, I'm glad you enjoyed the video. I enjoyed your proof. Limmy is a hoot!

In reply to by Alexander Johnson

Peter Adamson on 10 May 2019

Future contingents

Thanks, that was all very clever and I enjoyed it a lot. I especially like your idea of recording an event and then time traveling into the past, so the first argument. However I wonder whether that thought experiment founders on difficulties and paradoxes with time travel: as we know from Back to the Future, there are puzzles that arise. In particular, by transporting information from the present back into the past you are effectively turning a past moment into a "future" moment (because it is after the present moment in your own timeline) - in fact I believe this point was made in the recent Avengers movie! Not, admittedly, an irrefutable philosophical source but I think in this case it is right.

In general it is important to separate the issues of past _truth_ from issues of past _knowledge_. Inevitably paradoxes arise if you inform someone that they will do such and such an action freely, since as you say they can always thwart the predication, having heard it. Therefore I don't think it is coherent to imagine giving someone certain knowledge of what they will do in the future; I reckon we agree on this right? (And while we're making pop culture references all this is the reason why the plot of Minority Report makes no sense.)

Daniel Dover on 31 July 2017

Why God must see the future

So, there was a comment in the podcast as to why a medieval theologian wouldn't just suppose that God couldn't see the future (the future would be "unknowable" in the same sense that anything that doesn't exist is "unknowable"), and that wasn't really answered.  But clearly, the bible is full of prophets who offer prophecy given to them by God, in which they predict future events that the Bible also argues came true or will come true ("If the Jews don't shape up and follow God right, then destruction will be visited upon them!").  Thus, it seems natural to argue that God can see the future, unless one wants to argue that God isn't really seeing the future so much as stating his intent ("If the Jews don't shape up and follow God right, then God will visit destruction upon them!"), but this has some problems in how His prophecies are formulated (the bible often describes these as vivid visions of the future, where God shows someone specific things that will occur).  Thus, a certain amount of "the future exists and can be known" is implicit in the bible.

In reply to by Daniel Dover

Peter Adamson on 31 July 2017

God's foreknowledge

Yes, I think that's right - Biblical passages would surely have played a big part here. Probably also there was just reluctance to admit that God cannot do something we can imagine him doing. If God's omnipotence means he can do anything possible, then to deny his foreknowledge would require you to show why it is impossible for him to have foreknowledge. Which is a pretty tough ask!

Did you see by the way that all of episode 276 is also about this issue?

Erik Holkers on 4 January 2024

not necessary until we measure it

I ran into a similarity regarding the sea battle proposition.
Or more precisely, the issue that if it is already true or false now, the future would become necessary.

To me this looks similar to what I read about quantum systems (I am not an expert on this, far from it):

Superposition is the ability of a quantum system to be in multiple states at the same time until it is measured.
Meaning, it doesn't become true or false until we humans measure it. If we stay away, it stays in its superposition.

Same goes for the sea battle ? It has to become tomorrow first and us being present to measure ?
So the proposition is neither true nor false but could stay in its super position ?

Peter Adamson on 5 January 2024

Superimposed sea battle

That's a clever comparison: I would take that idea to boil down to one of the two main solutions found in the tradition, namely that one should simply deny that the proposition "There will be a sea battle tomorrow" is true or false. Only once the sea battle occurs is there any truth of the matter, just as there is no truth of the matter about where the particle is until one measures.

One thing I'd be slightly nervous of with your comparison is that we don't want to suggest that the sea battle problem has anything to do with our knowledge of whether there will be a sea battle problem; it is just about whether there is in fact (objectively, not for us) a truth about the future event before it happens. Your comparison doesn't violate that because in the physics case, there is no objective fact about the location. But talking about "measurement" could be misleading here: at with the sea battle, at no stage does it matter whether anyone knows anything about the event, even once it has happened. So you can run the whole thing with the proposition "Two asteroids in outer space will collide tomorrow, with no humans ever finding out about it" and both the problem and possible solutions will still work the same way. 

In reply to by Peter Adamson

Erik Holkers on 5 January 2024

superimposed sea battle

Hi Peter,
Thanks for explaining that. I get it that my idea doesn't fit completely and I did not intend to make you nervous. I used the term measuring deliberately in order to convey the idea that without what we are doing by measuring the event isn't there at all, it is neither true nor false (yet again I am no quantum expert) . Trying to know the outcome influences the whole issue, without measuring there is no outcome at all, neither a battle nor no battle. Not simply that we don't know left or right, but it isn't there. So basically, if we don't interfere by measuring, we effectively follow what you are saying, deny that the proposition "There will be a sea battle tomorrow" is true or false.   

In reply to by Erik Holkers

Peter Adamson on 5 January 2024

Measuring sea battles

I guess what I was trying to say is that "measuring" is not really the right way to think about it. The point is that the event happens, and if it is contingent then it is open (neither true nor false) whether it will happen until it does happen. Of course once it happens, then there is a truth about its happening, regardless whether anyone knows it happens. So your analogy works, but the analogy should be between "measuring position" and "an event occurring, whether or not anyone knows about it"; not between "measuring position" and "measuring/knowing about an event." See what I mean?

In reply to by Peter Adamson

Erik Holkers on 5 January 2024

Measuring sea battles

Yes, thanks again for the explanation.
And thanks for the marvellous podcast. 

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