Hear, hear.

OK, but this again is assuming that what constitutes "thing" and "parts" is uncontroversial and obvious. Do you want to say that Jill is a different "thing" if a couple of the microbes in her biome die between T1 and T2? What would make such an interpretation of "thing" attractive? The point is that we have to interpret it, because nothing in "A = A" will tell us how to do it. — J

I think I indicated that it's not philosophically uncontroversial. The point is that we assume that there are real things, and that the thing's identity, i.e. what the thing is, inheres within the thing itself, not in our descriptions or interpretations of the thing. A thing has temporal extension and changes as time passes, but this does not change the assumption made by the law of identity, that the thing has it's own identity at each passing moment, and always continues to be the very precise thing that it is regardless of how it changes.

I'm going to end the conversation here because you're shifting to an allowance for modal logic, but now asserting just pragmatic irrelevance. — Hanover

I kept telling you that I allow modal logic, I just dispute specific interpretations. So there is no shift on my part. I think perhaps you are just starting to understand what I've been trying to say.

I simply disagree with this assessment, and I question the thoughtfulness of the comment. If you think classic logic has relevance, then you simply can't dispense with modal logic because modal logic opens itself to logical issues beyond what can be handled in classic logic. Hypothetical counterfactuals result in vacuous truths in classic logic, and that is why modal logic is needed. — Hanover

I believe that counterfactuals are useful in the construction of philosophical theories and hypotheses, also in some probability theory, and likely in AI development. But I think counterfactuals generally do not have much of a practical application. However, counterfactuals are only a fringe part of modal logic (more like a curiousity) and modal logic in general has much practical application. I think that you are taking what I said about counterfactuals, as if I said it about modal logic in general.

I dont pretend there isn't nuance in these positions, but you don't elicit that nuance with your comments. You just hazard objections and see where they land, stubbornly insist upon the validity of your objections, and then eventually concede something or another to keep the conversation meandering. — Hanover

Interesting opinion.

With Wiiki, Google, the SEP, countless other online resources, and even ChapGpt to sort through all this, we should be able to engage in this conversation at a more elevated level and share among ourselves areas of real confusion. So maybe spend a few days on your own with an open mind toward understanding the basis of the modal logic enterprise before critiquing it. — Hanover

I think that you and Banno are not interested in discussing the underlying assumptions which support modal logic, and the appropriate interpretations, like I am. Instead you just want to proceed into discussing formal structure, which I am not interested in. So there is a divergence of interest between us.

That's quite a misrepresentation, given that what I did was to point to how temporal necessity can itself be accommodated by formal modal logic. — Banno

Then why did you give an example of what Hanover called "metaphysical necessity", ("if it is necessary it could not have been otherwise"), and reject my use of temporal necessity, ("it cannot be changed, but could have been otherwise")? You rejected my use of temporal "necessity", saying I must speak in terms of metaphysical "necessity", and now you come back and say that "temporal necessity" is actually provided for in modal logic.

The other supposed objections you raise have either been or can be dealt with within the standard framework. In particular, the treatment of accessibility answers your main misunderstanding. Explaining this repeatedly is tedious. — Banno

I believe, the way that you employ "actual world" in your example of Caesar crossing the Rubicon, is not actually a fair representation of how modal logic would be most useful in the context of that example. Consider the following:

Of all the possibilities (so-called possible worlds) to be entertained, we cannot assume any particular one to be the actual. The only actual world is the here and now, the truth of "what is" in our current condition, at the present. And, we do not have the means to make a direct relation from any assumed actual world of now, to that ancient time. So, we may have one version of history which says Caesar crossed the Rubicon at a specific time. Another historian might say that Caesar was in Rome at that time. Another might put him somewhere else. All of these are possibilities (possible worlds). Then we can collect other evidence of Caesar's movements, and possible whereabouts in that temporal proximity, and treat all the distinct pieces of evidence as further possible worlds. When we relate all these distinct possibilities (possible worlds), we judge for consistency between them, and this gives us the best probability of determining what was actually the case. Notice, that we do not determine what was actually the case, we determine the most probable solution. I believe the best interpretations, and most productive applications of modal logic completely dispense with the idea of an actual world, dealing completely within the possible, making judgements based on probability. This is a completely break from the logical structure which assumes truth value, what is "probable" is based on consistency.

Compounding your own confusion.

The law of diminishing returns applies. Have fun.

. I would then also add free will as another possible way to get contingency....Overall, it seems we are almost in agreement, except for the possibility of inherent existence and quantum. — A Christian Philosophy

I agree that IF libertarian free will exists, then it is a source of contingency. Would you agree that IF quantum collapse is indeterminate, the it is a source of contingency?

If we found out that all outcomes in the actual world occur out of necessity, then conceiving a possible world with some different outcome would necessarily have a logical error in it. — A Christian Philosophy

Conceiving of a counterfactual world does not imply that world is physically or metaphysically possible.

Examples:
1.I can conceive of a possible world in which earth has 2 moons instead of 1. Is that world physically possible? No, because the single moon is present as a result of the deterministic laws of nature. There is no source of contingency in the physical world to account for the counterfactual 2-moon earth. Conceivability doesn't align with what is physically possible. In terms of possible worlds: the set of conceptually possible worlds is not identical to the set of physically possible worlds.

2. Assume the PSR is metaphysically necessary. I can nevertheless conceive of a world in which the PSR is false: so there is a conceptually possible world in which the (metaphysically necessary) PSR is false.

No, because the single moon is present as a result of the deterministic laws of nature. — Relativist

Sorry to but in, but surely the number of moons a planet has, and the number of planets a solar system have, is not determined by any laws of nature. What is determined is how they orbit their stars and planets. What could not occur would be an orbital path not determined by those laws.

Sorry to but in, but surely the number of moons a planet has, and the number of planets a solar system have, is not determined by any laws of nature. — Wayfarer

It's determined by the set of physical steps that led to the existence of the solar system. Each step is necessitated by laws of nature. Laws of nature necessitate their outcome. (We're assuming QM is deterministic). You'd have to assume random things happen for no reason, contrary to the PSR.

We're assuming QM is deterministic). You'd have to assume random things happen for no reason, contrary to the PSR. — Relativist

But I think that's a huge assumption. Even if it were true the amount of information one would have to have to calculate how many satellites a given planet could have is unknowable in practice, and it is known there are planets with more than one satellite (even other planets in our solar system.) The OP frames the relationship between PSR and determinism as binary—either every event is strictly determined, or not. But the relationship isn’t that simple. The principle of sufficient reason claims that everything has a reason or sufficient condition. However, that reason doesn't necessarily dictate a single, fixed outcome in all cases, it might only provide a range of possibilities (which is exactly what the Schrodinger equation does, come to think of it.) Meaning there can be degrees of likelihood, within a range (like, the particle will be registered, but it won't be a watermelon.)

And furthermore, natural laws are based on idealisations and abstractions - point particles, frictionless planes, and so on - which we don't encounter in reality. So in short, I don't see an a priori reason why a planet such as ours doesn't have two moons - it is a contigent fact.

What is determined is how they orbit their stars and planets. — Wayfarer

Not determined so much as described. The motion precedes the "law," and supersedes it, too. The law was decided as a result of looking at the motion, and is changed in the light of further observation.

So which is doing the "determining"?

Sure—but I think we have to distinguish between how laws are discovered (epistemology) and what they describe about the world (ontology). You're right that laws like Newton's were formulated after observing motion, and that our models change with better observations. But that doesn't necessarily mean motion itself is lawless or "undetermined" in some deeper sense.

In the Newtonian framework—within its applicable range—the laws don't just describe motion, they enable precise prediction. If I know the mass, velocity, and position of a satellite, and I apply Newton’s equations, I can calculate where it will be tomorrow, and I’ll be right (at least to an excellent approximation). That’s more than just post hoc description—it reflects an underlying law-like regularity.

Granted, this breaks down at relativistic scales or in quantum domains—but that’s part of the point. Lawfulness can be domain-specific, and even in more advanced physics, the idea of constraint or structure doesn't vanish. It just becomes subtler. So I’d still say there’s a real sense in which orbital motion is determined—at least within the scope of classical mechanics.

So: yes, our formulations of the laws are historically contingent and always open to revision. But the regularities they describe are not arbitrary. They're what allow us to build spacecraft that actually arrive at their destinations. The laws of motion can predict how moons orbit planets, once they exist—but those same laws don’t determine how many moons a given planet will have. That depends on many contingent factors—collisions, accretion history, nearby bodies, etc.—that fall outside the scope of deterministic prediction. There’s lawfulness in how systems behave, but not everything that happens is fixed by those laws alone.

I think the interesting philosophical point is precisely the sense in which the laws of nature seem true a priori, irrespective of experience. I mean, whenever something is suggested that might not obey those laws on this forum, merry hell usually follows :-)

the laws don't just describe motion, they enable precise prediction. — Wayfarer

The law doesn't enable anything much. Except text book, perhaps. They do describe motion precisely, enabling prediction. Best avoid giving then the ontological status of involved in causation. Reification and all that. So better not to talk of enabling.

None of which makes the descriptions arbitrary.

I think the interesting philosophical point is precisely the sense in which the laws of nature seem true a priori, irrespective of experience. I mean, whenever something is suggested that might not obey those laws on this forum, merry hell usually follows :-) — Wayfarer

"seem true a priori"?

Surely not. Your intuitions can't be that bad.

Ok not ‘seem’. ‘Are’.

That'll save on the physics budget then. No need for all that experimental machinery if they can work it out by deduction. Pencil and paper from now on.

Even if it were true the amount of information one would have to have to calculate how many satellites a given planet could have is unknowable in practice, — Wayfarer

We're discussing possibility/impossibility of a state of affairs, not the computability.

And furthermore, natural laws are based on idealisations and abstractions — Wayfarer

That conflates textbook laws of physics with ontological laws of nature. As you know, I am a law realist. The present discussion is an alleged proof of God's existence, and I'm demonstrating that the proof depends on debatable metaphysical assumptions. I'm not trying to prove anything, other than the fact that conclusion is epistemically contingent on unproveable metaphysical assumptions.

Still don't see any justification for the claim that the Earth could have only one moon as 'a matter of natural law'.

You'd have to assume random things happen for no reason, contrary to the PSR. — Relativist

Just remind me again why Einstein said he doesn't believe that God plays dice?

The point is that we assume that there are real things, and that the thing's identity, i.e. what the thing is, inheres within the thing itself, not in our descriptions or interpretations of the thing. — Metaphysician Undercover

But that's just what I'm questioning. It's precisely our interpretation of what "Jill" is going to encompass that will tell us what the "real thing" is. I assume you're not saying that there is some correct construal of "Jill" that is independent of interpretation. But in any case, I'm glad to see you backing off from the idea that identity has to include "all properties, essential and accidental".

I assume you're not saying that there is some correct construal of "Jill" that is independent of interpretation. — J

No, that is what I am saying. The law of identity, "a thing is the same as itself" indicates that there is an identity ("correct construal" if you like), which inheres within the the thing itself, therefore independent of interpretation.

But in any case, I'm glad to see you backing off from the idea that identity has to include "all properties, essential and accidental". — J

Why would you think that I am backing off from that? It's exactly what the law of identity indicates, proper identity inheres within the thing, as the complete form, all properties, essential and accidental, rather than an abstraction consisting of what is perceived to be essential.

The law of identity, "a thing is the same as itself" indicates that there is an identity ("correct construal" if you like), which inheres within the the thing itself, therefore independent of interpretation. — Metaphysician Undercover

In classical philosophy—especially in Platonic and scholastic traditions—particulars are not intelligible in and of themselves, but only insofar as they participate in or receive a form or essence. Their identity is not something they generate, but something they manifest - in the theistic traditions, bestowed by the Creator.

This contrasts with modern metaphysical assumptions, which often treat particulars as having an independent reality. Eckhart: “creatures are mere nothings”. From within this perspective, the mind doesn’t impose identity, but recognizes it through a kind of intellectual illumination that reveals a deeper metaphysical order (by recognising the form or what-it-is-ness of the particular being.)

It's Aristotle who designated the identity of the individual as within the individual itself, commonly known as the law of identity, "a thing is the same as itself". This identity supports the reality of primary substance. I think we discussed this before, and you didn't accept that Aristotle recognized the identity of the particular.

The point of the scholastics is that the proper identity of the thing is not intelligible to us, human beings. We can only know things through abstraction, which does not grasp the true identity. The identity of particular things is, however, intelligible to God.

Just remind me again why Einstein said he doesn't believe that God plays dice? — Wayfarer

I'm sure that there are better ways of putting this, but the short answer is that Einstein said this because he believed that there was some underlying mechanism that would (in some manner) eliminate the uncertainty from the uncertainty principle. To the best of our current scientific knowledge, Einstein was mistaken in this belief.

As an aside (and apologies if I'm telling you something you already know) Einstein did not have any conventional religious beliefs. He was sort of a Spinoza-ist.

It's Aristotle who designated the identity of the individual as within the individual itself, commonly known as the law of identity, "a thing is the same as itself". This identity supports the reality of primary substance. I think we discussed this before, and you didn't accept that Aristotle recognized the identity of the particular. — Metaphysician Undercover

Yes, the law of identity (a=a) is a logical principle—a tautology that belongs to the structure of thought and language. It tells us something about the consistency of our terms, but not about the ontological self-sufficiency of particulars. To read it as a statement about the intrinsic metaphysical identity of beings is to conflate logic with ontology.

When Aristotle discusses primary substance in the Categories, he's not saying that the identity of the individual particular is simply in the particular in some absolute sense. Rather, he's marking it as that which is neither said of nor in a subject—that is, the individual concrete thing, like “this man” or “this horse.” (ref). But even so, its intelligibility depends on form, not on its specific particularity.

Moreover, Aristotle’s deeper metaphysics—in the Metaphysics and De Anima—makes clear that a substance’s what-it-is is grasped through form, not through brute particularity. So it’s not that the individual grounds its identity in itself, but that its being is composed of matter and form, and its intelligibility lies primarily in the formal principle, not in the sheer fact of its being “this one.”

The law of identity is a logical framework that presupposes ontological grounding—it doesn't establish it.

Sure, right on both counts. My bad for introducing it, as quantum weirdness is a gauranteed thread de-railer, except for its undeniable relevance to questions of determinism.

Surely not. Your intuitions can't be that bad. — Banno

Yes, acknowledge that they're not true a priori. Still struggling to see how the laws of motion would dictate that the Earth couldn't have two satellites, when other planets do.

Yes, the law of identity (a=a) is a logical principle—a tautology that belongs to the structure of thought and language. It tells us something about the consistency of our terms, but not about the ontological self-sufficiency of particulars. To read it as a statement about the intrinsic metaphysical identity of beings is to conflate logic with ontology. — Wayfarer

Actually, you might research this. The law of identity, "a thing is the same as itself", as derived from Aristotle, is completely different from the modern presentation by logicians, of "A=A". How do you interpret "a thing is the same as itself" as being a statement about consistency in our terms, rather than what it obviously is, a statement about things, the intrinsic metaphysical identity of beings?

When Aristotle discusses primary substance in the Categories, he's not saying that the identity of the individual particular is simply in the particular in some absolute sense. — Wayfarer

Aristotle's best discussion of identity is in his Metaphysics. There is much to read because it stretches over a number of books. I believe he starts in earnest where he says that the fundamental question of being is not the question of why there is something rather than nothing, but why there is what there is, rather than something else. This amounts to the question of why an individual thing, and every particular, individual thing, is what it is, rather than something else. The law of identity, that a thing is necessarily the thing that it is, and it is impossible that any thing is something other than the thing that it is, provides his starting assumption.

Moreover, Aristotle’s deeper metaphysics—in the Metaphysics and De Anima—makes clear that a substance’s what-it-is is grasped through form, not through brute particularity. So it’s not that the individual grounds its identity in itself, but that its being is composed of matter and form, and its intelligibility lies primarily in the formal principle, not in the sheer fact of its being “this one.” — Wayfarer

According to Aristotle's Metaphysics, each individual thing has a form which is proper to itself and only itself. This form, as the form of the material thing, is complete with all accidentals. Also, he argues that since things are composed of matter and form, and form is what makes the thing what it is rather than something else, substance belongs to the form. Pure matter would have nothing to differentiate itself, providing for no individual things, therefore no substance.

The law of identity is a logical framework that presupposes ontological grounding—it doesn't establish it. — Wayfarer

I really think you ought to investigate further, exactly what the law of identity is, in its classical form.

I’d suggest that there really isn’t a “classical form” of the law of identity in the sense you seem to mean. Aristotle doesn’t formulate such a law as a formal axiom—his concern is metaphysical, not symbolic. The modern statement “A is A” or “x = x” comes from a much later tradition, shaped by formal logic and set theory, not Aristotle’s ontology of substance and form. To read Aristotle as if he were simply asserting the self-contained identity of particulars is to read him through a modern lens that doesn’t fit.

According to Aristotle's Metaphysics, each individual thing has a form which is proper to itself and only itself. — Metaphysician Undercover

Aristotle's position is that form is what makes an individual intelligible as a member of a kind. It’s not that each individual has a completely unique form proper to itself, but rather that many individuals share a common form—what we’d call a species or essence. What individuates one member of a species from another is matter, not form - matter is what individuates them. To suggest that each individual has a form unique to itself closer to nominalism.

That's as far as I'm going to go. You've been on about this for years, as some kind of self-designated expert, but I'm never persuaded by your polemics, even while I don't claim to be an expert myself.

That god can create any possible world does not explain why he created this one. And if god created this world out of necessity, then it could not be other than it is. Modal collapse. — Banno

As per the OP, there are 3 types of reasons that fulfill the PSR. Reasons type 1 and type 3 are necessary reasons. Type 2 is a contingent reason and applies to agents with free will. As long as the agent has a purpose to decide what they decide, then the PSR is fulfilled, despite the choice being contingent. In our case, the OG would have a purpose to stipulate the actual world, even if that purpose is unknown to us.

I agree that IF libertarian free will exists, then it is a source of contingency. Would you agree that IF quantum collapse is indeterminate, the it is a source of contingency? — Relativist

Yes, I agree with that in theory.

Conceiving of a counterfactual world does not imply that world is physically or metaphysically possible. — Relativist

I suppose that's true; just like we are able to talk about impossible worlds. Nevertheless, modal collapse should still be avoided when we talk about metaphysically possible worlds.

There is no source of contingency in the physical world to account for the counterfactual 2-moon earth. — Relativist

Still struggling to see how the laws of motion would dictate that the Earth couldn't have two satellites, when other planets do. — Wayfarer

My two cents. I think what Relativist is saying is that, assuming deterministic laws of nature, then there would have been no possibility of having two moons in the past or in the present because it did not happen. But there could still be two moons orbiting the Earth in accordance to deterministic laws of nature in the future. E.g., the current moon splits in two; another large body passes by and starts orbiting the Earth; etc.

Interesting take!
First is the obvious problem: natural laws falling into external contingency. The laws are, as you point out, fundamental. They exist simply by their fundamental nature that need not be an external cause. PSR should also, I believe, not be presupposed by an external contingent reason as it must as well be subject to PSR. This external contingent reason would only exist if it is treated as fundamental.

and for a specific purpose — A Christian Philosophy

This is automatically true if you presuppose PSR. This should be true for all types, not necessarily requiring a free-will system.

In addition, I feel there is a lack of distinction between existential reason (reason for existence) and purpose (reason to exist) in "Man itself" section, although I feel that it is irrelevant to the core argument.

I suppose that's true; just like we are able to talk about impossible worlds. Nevertheless, modal collapse should still be avoided when we talk about metaphysically possible worlds. — A Christian Philosophy

I continue to take issue with the notion that "modal collapse" must be avoided. I believe that modal collapse translates to necessitarianism in ontology: the notion that everything that exists could not have failed to exist, and that there are no non-actual possibilities (non-actual possibility= something that could have happened, but did not).

What would prevent necessitarianism from being true is some source(s) of contingency. No proposed source of contingency can be proven. You correctly noted that quantum collapse isn't necessarily contingent, and I pointed out that libertarian free will does not necesarily exist.

. To read Aristotle as if he were simply asserting the self-contained identity of particulars is to read him through a modern lens that doesn’t fit

...

Aristotle's position is that form is what makes an individual intelligible as a member of a kind. — Wayfarer

This is simply wrong, and not at all representative of what is actually found in Aristotle's Metaphysics. I've provided much evidence for you, in our past discussions on this matter, but you seem to have a strong bias which inclines you to ignore the evidence. It's well known that Aristotle's hylomorphism provides an approach to the substance of individuals, and the form of the individual is responsible for what it is, not just its type, but "what it is" in a complete sense. It would be a significant inconsistency, making Aristotle's metaphysics unintelligible, if form was responsible for the type, and matter was responsible for individual features. Notice that the suggested "prime matter" could have no features whatsoever, and would be absolutely unintelligible. This implies that all features of an individual, including those unique to the individual, which make a thing the particular thing which it is, must be formal.

What individuates one member of a species from another is matter, not form - matter is what individuates them. To suggest that each individual has a form unique to itself closer to nominalism. — Wayfarer

This statement demonstrates a misunderstanding of "matter". Matter itself cannot have any individuating features. That's what makes it fundamentally unintelligible. The separation between matter and form is what provides the distinction between what is in principle intelligible, and what is not intelligible. The fact that some features of an individual are not intelligible to the human intellect does not render them unintelligible in an absolute sense, because a higher intellect might grasp them. Therefore all the features of individuation, which make an individual what it is, whether its genus, species, variety, or the unique features of the particular, must be formal. To maintain consistency, all individuating features must be formal.

This user has been deleted and all their posts removed.

Yes, the law of identity (a=a) is a logical principle—a tautology that belongs to the structure of thought and language. It tells us something about the consistency of our terms, but not about the ontological self-sufficiency of particulars. To read it as a statement about the intrinsic metaphysical identity of beings is to conflate logic with ontology. — Wayfarer

Exactly.

The modern statement “A is A” or “x = x” comes from a much later tradition, shaped by formal logic and set theory, not Aristotle’s ontology of substance and form. To read Aristotle as if he were simply asserting the self-contained identity of particulars is to read him through a modern lens that doesn’t fit. — Wayfarer

And this.

"A = A" can tell us nothing about what we ought to substitute for A. It's not about being or ontology at all.