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If we say there are three types of time — historical time, chronological time, and biological time —, the main character is younger than his daughter in all but historical time. — Lionino

I would say there are historical (Earth or chronological) time and phenomenological time. If biological processes would be slowed down, reduced to almost zero at near light speeds, what would a person on a craft travelling at such speeds experience? Such travel may well be physically impossible in any case, but allowing for the sake of argument its possibility, I can only imagine that during such a journey, even if it lasted a thousand years, the passengers would experience almost no time, or even no time at all, if travelling at light speed.

So, yes if that were possible then the main character would be biologically younger than his long dead daughter. On the other hand, since Earth time is really what counts for us, we would say he has been gone for a thousand years, and is thus one thousand plus years old, even though relatively unaged.

Should we count age as being the time of duration or physical change? — Janus

There's a fable I was acquainted with as a kid in which the hero overcomes many an obstacle to at long last arrive in a kingdom where life occurs without death and without aging (though physical changes generally speaking do occur there: folks move about, talk, etc.). Being a magical place, he looses track of time. Nevertheless, after what by all accounts is a short stay there, he becomes nostalgic and wants to see his family again - not having seen them since the commencement of his journey a long time back. Though warned against leaving the kingdom, he leaves to return to his homeland. Once he arrives back from where he started his quest, he finds that eons had gone by since his departure, with everything he once knew and loved now gone.

At this juncture in the story, should we deem the protagonist to be millennia old or, conversely, twenty-some years old?

Long story short, I don't find this question to be answerable via any one of the two options presented alone. Rather, I find the issue of his age fully relative to the conceptual context addressed. Such that in the story both appraisals of his age are simultaneously actual but in different respects.

And, although I personally find this fable far more telling in terms of possible metaphysics of time (i.e., of duration), the same can be said of Highlander movies or of any vampire story: that the the character lives for hundreds of years or more while remaining of a constant age makes conceptual (else, metaphysical) sense. These stories would all be utterly unintelligible otherwise.

This to better illustrate the following stance: The answer to the question of whether "a child can be older than her parents" - this as a metaphysical possibility - will be relative to the semantics employed for the concept of age.

So, in durational terms she is always going to be older than her daughter, and since the very meanings of 'mother' and 'daughter' presuppose that the mother exists antecedently to the daughter, then to say that the child could be older than the mother would involve a logical contradiction. — Janus

As per my previous post, I agree with this in full.

An addendum for improved clearness as regards my last post, just in case it might be needed:

In the fable presented, the protagonist’s age as measured by his own personally experienced duration of time will factually be that of twenty-some years. This though, in the fable, relative to the duration of time as would be measured by all those he departed from on his initial quest, he will factually be millennia old. In both cases his age is yet measured by duration, but this relative to the vantages of different actual or (being now dead) potential observers. (This as can be just as validly said of various scenarios concerning time dilation within the theory of relativity.)

Also noteworthy, physical changes occur in both of these duration-grounded appraisals of the protagonist’s age. So the division between age as measured by “duration of time” and by “physical changes” becomes largely spurious - although I do get what you intend by the dichotomy.

Secondly, and entwined with the just mentioned, there then will not be one objectively true vantage point of the protagonist’s age, this such that the other vantage point becomes falsity. The protagonist will hence factually be both ages at the same time, with each age being factual from a different vantage point.

As regards metaphysical possibilities, this then to me sets the fable apart from the Adeline movie scenario - as well as from vampire stories, etc. - in terms to the metaphysics of time. It basically seems to addresses the metaphysics behind the theory of relativity without the implied physicalism (and the block universe model) that is typically ascribed to the theory.

Which then directly ties in with this:

So, yes if that were possible then the main character would be biologically younger than his long dead daughter. On the other hand, since Earth time is really what counts for us, we would say he has been gone for a thousand years, and is thus one thousand plus years old, even though relatively unaged. — Janus

When impartially addressed, neither the character's vantage of his own age nor our own Earth-dwelling vantage of his age is privileged. Again culminating in the conclusion that both appraisals of his age are true, i.e. conform to what is factual - but this from different vantage points of observation.

All this stands in contrast to the notion that there is a universally applicable, objective, singular time frame.

But this is not to imply there is a discord between what I've said and what you've expressed.

In the fable presented, the protagonist’s age as measured by his own personally experienced duration of time will factually be that of twenty-some years. This though, in the fable, relative to the duration of time as would be measured by all those he departed — javra

This puts me in mind of some of Kant's CPR i've gone over in the alst couple of days.
The relation of time is individual in that an external impression of another person doesn't exist in their time, it exists in the perceiver's time. I would think that this means we can just see any subjective notion of time as legitimate. It only exists as a relation, so there's no other benchmark.

Is that silly, or somewhat reasonable?

This puts me in mind of some of Kant's CPR i've gone over in the alst couple of days.
The relation of time is individual in that an external impression of another person doesn't exist in their time, it exists in the perceiver's time. I would think that this means we can just see any subjective notion of time as legitimate. It only exists as a relation, so there's no other benchmark. — AmadeusD

It is commonly enough known that we perceive time in subjective manners (the linked Wikipedia article gives a nice presentation). This I think fits into part of what you are saying. But this can’t then be the only benchmark for time, otherwise there would be no way of discerning between time which is subjectively perceived (and which can vary by individual) and that time which is objectively occurring (and is equally applicable to all causally interacting, or else causally entwined, observers).

As concerns objective time, however, the same dichotomy between a relativistic time and cosmically absolute time will present itself. With all indications now pointing to time being relativistic rather than absolute. So, in extreme time dilation scenarios, for one example, an individual can still have two distinct ages that are both objective (and hence not subjective) by breaking away from a commonly shared time frame (for example, the time frame that Earth dwellers more or less all inhabit (though minor forms of time relativity still apply here on Earth)) and then subsequently rejoining it.

To illustrate the distinction between subjective and objective time via a simple example: In a given conversation, time might by going slow for one individual and might be going fast for the other (this due to each individual’s separate chronoception) but will nevertheless be commonly applicable (hence, impartially applicable and, in at least this sense, objective) to both individuals in terms of the back-and-forth dialogue of the conversation - e.g., both will know who said what prior to whose reply, etc., thereby facilitating the possibility of a conversation. And if there were a clock present to both during the conversation, both could potentially pinpoint at which commonly shared, objective time a certain statement was made in durational relation to some other - this despite the differences in chronoception between the two individuals.

Its a very complex topic, this metaphysics of time. But that's my best answer so far.

As concerns objective time, however, the same dichotomy between a relativistic time and cosmically absolute time will present itself. With all indications now pointing to time being relativistic rather than absolute. — javra

And yet the claim is that the Universe began around 14 billion years ago. Time perhaps does not exist apart from change, and when you think about it the general durations of processes of change probably don't vary that significantly because no macro-objects are travelling at anywhere near the speed of light, and they also are not subject to massive time variations due to gravity either.

And yet the claim is that the Universe began around 14 billion years ago. — Janus

Unless I'm mistaken, there is no other way that estimate can be established other than via the theory of relativity - coupled, of course, with empirical evidence. So instead of contradicting the relativity of time, it will be one derivation from it.

Right, but what I was angling at is that the age of the Universe would not vary depending on where you are in it; there would seem to be a sense in which there is a current state of the Universe. And in general, when we talk about the age of anything, existing things which came into being earlier than other existing things are considered to be the older. On this criterion a daughter could never be older than her mother while they are both still alive, although of cause the daughter could live to a greater age.

And in general, when we talk about the age of anything, existing things which came into being earlier than other existing things are considered to be the older. On this criterion a daughter could never be older than her mother while they are both still alive, although of cause the daughter could live to a greater age. — Janus

I've already agreed to this, upheld it even before you mentioned it. But I don't see how this then contradicts the theory of relativity as regards a person potentially holding two actual ages in different respects - given the circumstances previously specified.

So that we're on the same page in terms of the theory of relativity's reality:

How does this connect with General Relativity and GPS? As predicted by Einstein’s theory, clocks under the force of gravity run at a slower rate than clocks viewed from a distant region experiencing weaker gravity. This means that clocks on Earth observed from orbiting satellites run at a slower rate. To have the high precision needed for GPS, this effect needs to be taken into account or there will be small differences in time that would add up quickly, calculating inaccurate positions. — https://www.nasa.gov/image-article/einsteins-theory-of-relativity-critical-gps-seen-distant-stars/

The theory of relativity does operate in terms of Earths own otherwise general time frame. So if travel even between different solar systems were to be possible, it would operate in these circumstances as well.

Yes, if the theory of relativity is in fact correct it operates everywhere. Since the different gravitational forces would not make for much of a difference, and it may well be impossible for objects to travel at anywhere near the speed of light, such thought experiments as would allow for huge differences in the progress of biological processes, and hence significant differences in aging probably remain in the realm of fiction or fantasy.

Since the different gravitational forces would not make for much of a difference, — Janus

The example I just gave of GPS evidences the significant difference between the gravitational force that a satellite is in and the gravitational force that a Earth-bound human is in. But I guess considering what is a "significant difference in different gravitational forces" would embark us too far astray.

and hence significant differences in aging probably remain in the realm of fiction or fantasy. — Janus

... and in the realm of metaphysical possibility, which this thread is in part about.

But I guess considering what is a "significant difference in different gravitational forces" would embark us too far astray — javra

I would say it would be difference great enough to make a significant difference to biological "age".

... and in the realm of metaphysical possibility, which this thread is in part about. — javra

We don't know what is metaphysically possible, and we only know what is physically possible given the assumption that our understanding of natural laws is correct and comprehensive.

We don't know what is metaphysically possible, — Janus

As a friendly reminder, we do know that different ontologies are metaphysically possible.

Although we also know logically that contradictory ontologies (e.g., that of physicalism vs. that of idealism vs. that of substance dualism) cannot all be accurate models of the physical, or better yet actual, world (needless to add, this at the same time and in the same respect).

As a friendly reminder, we do know that different ontologies are metaphysically possible. — javra

How do we know that?

I'll say that, if by no other means, then via acquaintance with there so being different ontologies out there, all of which are metaphysical possibilities regarding what the actual world in fact is. These are all metaphysically possible rather than physically possible in the same way that a possible world is metaphysically possible rather than physically possible - only that in the case of ontologies, one of them might be a more accurate mapping of the actual than the others.

Why ask such a question?

It seems we may have very different notions of what 'metaphysically possible' means. As I see it, if there is only one world then what is metaphysically possible would just be what is physically or actually possible. If there were other worlds, then different sets of physical laws might be metaphysically possible and actual. If there were a non-physical world, then whatever constraints operated in that world would be metaphysical (and of course logical) constraints. But all of this is only, for us, in the realm of the imagination, pure speculation: we have no way of knowing otherwise. If you have an alternative understanding, I'd be happy to hear about it.

If you have an alternative understanding, I'd be happy to hear about it. — Janus

My take was stated in this post in the thread, which is itself based on this SEP entry (you can quickly look at the SEP entry's section 1's two definitions of metaphysical possibility).

Thanks...these are the definitions given there:

p is metaphysically possible iff p is true in at least one possible world.
p is metaphysically necessary iff p is true in all possible worlds.

p is metaphysically possible iff p is consistent with the laws of metaphysics.
p is metaphysically necessary iff p follows from the laws of metaphysics.

I see the first as being circular and uninformative, because we don't know what worlds (if any other than our own) are possible unless we count possibility as being simply what we can coherently imagine.

I see the second as also being uninformative because we don't know what the laws of metaphysics are, unless, again, they are what we can imagine without contradiction.

In both cases if metaphysical possibility is just what we can, without contradiction, imagine, then metaphysical possibility would seem to collapse into logical possibility.

The meaning of modalities is in their use, which is inadequately represented by picture-theories of modalities, especially the silly Venn diagrams stemming from the naive depiction physical possibilities as being a proper subset of metaphysical or logical possibilities.

First of all, are modalities empirical claims about reality, or they normative rules of convention that refer to the use and interpretation of a model, or are they both? And besides, how does the empirical content of a model relate to the application of it's rules? Can Kripkean semantics, or any other plum-pudding depiction of possible worlds do justice to the complicated use meaning of modalities?

Consider the fact that physical impossibility cannot be empirically falsified, at least not in the naive way that people presume. For example, the physical impossibility of faster than light travel cannot be directly tested nor understood by measuring the speeds of various objects, for we cannot observe what isn't observable, and the literal claim that nothing can travel faster than the speed of light cannot be directly verified by any finite number of experiments. Nor can a philosopher directly imagine faster than light travel in a thought experiment (for what would that look like, exactly?). So both the empirical and theoretical meaning of the impossibility of faster than light travel is far from straightforward and definitely not obvious. Furthermore, the literal English meaning of "faster than light travel" cannot even be translated into the language of Special Relativity, for SR maps the English sentence "faster than light travel" to infinite Lorentz factors that are extensionally meaningless.

The empirical meaning of SR is demonstrated by the experiment and results of the Michelson Morley experiment that partly motivated it. This empirical meaning does not refer in any obvious way to the sentiment that "faster-than light travel is impossible". If a physicist is asked to describe the meaning of this impossibility, he will likely refer to empirically observable Lorentzian relations that he argues are expected to hold between observable events. In other words, his use-meaning of the "physically impossible" is in terms of the physically possible!

So physical impossibilities shouldn't be thought of in terms of impossible worlds, but rather as referring to the application of a linguistic-convention that supports the empirical interpretation of language.

I'll say that, if by no other means, then via acquaintance with there so being different ontologies out there — javra

There are different ontological theories; there is one ontological subject and object of study, which is existence. Having different ontological hypotheses doesn't alter the nature of the real.

What is possibility? It is "possible" that string theory is true, e.g. that it aligns with reality. It is possible that a rolled dice will come up six. Which only means that, in the actual unfolding of actual events someone rolls the dice and it comes up six. It doesn't mean that there actually are alternate realities in which every case of every event is realized. Ex hypothesi, if these alternate realities exist, they are mutually exclusive, in which case, they represent metaphysically exclusive cases. So there is still only one overriding metaphysics, that which governs each exclusive modal set. That spirals off into an infinite set of infinite universes, which is absurd. The whole nature of the universe, as quantum physics explores, is to consume these possibilities. Information decoheres from a state of superpositions to realized specific configurations which are "preferred" and which, qua pointer states, correlate with specific physical properties.

what would something metaphysically impossible but logically possible be? — Lionino

It's logically possible that abstract objects exist, but their existence is metaphysically impossible if physicalism is true.

In general one would judge as metaphysically possible, anything that is consistent with one's prior ontological commitments. If contradicted by ontological commitments, you'd judge it metaphysically impossible.

If you prefer to judge metaphysical possibility from a perspective that's devoid of ontological commitments, then metaphysical possibility = broadly logical possibility.

The empirical meaning of SR is demonstrated by the experiment and results of the Michelson Morley experiment that partly motivated it. This empirical meaning does not refer in any obvious way to the sentiment that "faster-than light travel is impossible". If a physicist is asked to describe the meaning of this impossibility, he will likely refer to empirically observable Lorentzian relations that he argues are expected to hold between observable events. In other words, his use-meaning of the "physically impossible" is in terms of the physically possible!

So physical impossibilities shouldn't be thought of in terms of impossible worlds, but rather as referring to the application of a linguistic-convention that supports the empirical interpretation of language. — sime

Of course, I must agree that physical impossibility is grounded in physical possibility; there is that which is physically possible, and the rest is not; so I'm not sure what you are aiming at with that.

I realize that an hypothesis such as that travel faster than light is impossible can never be verified by any number of observations. I was only concerned with the notion that there should, or even merely might, be physical impossibilities, regardless of whether we can know what they are or even whether there are such impossibilities.

If we adhere to the idea of universal natural law and assume that what we understand about that law is valid and reflects necessary or universal invariances, then within that context, we can talk about physical impossibilities. But the caveat will always be 'given that the laws of nature are themselves invariant".

The idea that there might be worlds (or universes) which enjoy very different laws would then transcend this notion of physical impossibility which is based on our familiar laws. So, I would refer to that as metaphysical possibility. The question then would be as to whether there should or must be any constraints on metaphysical possibility other than those of a merely logical nature.

Being fundamentally a skeptic, of course I will answer that we can raise these kinds of logically derived questions, but we cannot decidedly answer them. They remain exercises of the speculative imagination.

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I would also raise that if physicalism is true, metaphysical possibility = physical possibility. — Lionino

100% agree.

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If we adhere to the idea of universal natural law and assume that what we understand about that law is valid and reflects necessary or universal invariances, then within that context, we can talk about physical impossibilities. But the caveat will always be 'given that the laws of nature are themselves invariant". — Janus

If naturalism is true, and there are laws of nature, I suggest the true natural laws would be invariant. The way they manifest might be contingent on local conditions. That's why I think its important to refer to laws of nature, as you have done, rather than the laws of physics- which are based on our current understanding, and subject to revision as we learn more.

The laws of metaphysics do not follow necessarily from logical possibility. — Lionino

I agree with you, but would just repeat that we don't, can't, know what the laws of metaphysics (if there be such) are. Logical possibility informs us only about what is possible, not about what is necessary.

If naturalism is true, and there are laws of nature, I suggest the true natural laws would be invariant. The way they manifest might be contingent on local conditions. That's why I think its important to refer to laws of nature, as you have done, rather than the laws of physics- which are based on our current understanding, and subject to revision as we learn more. — Relativist

The Laws of nature may evolve (as Peirce thought) but if that were so they would still be invariant over long periods (unless there were some kind of "punctuated evolution" as S J Gould postulated in regard to biological evolution). The laws of nature may be understood simply as the 'observed habits of nature as formulated by us).

There are different ontological theories; there is one ontological subject and object of study, which is existence. Having different ontological hypotheses doesn't alter the nature of the real. — Pantagruel

Of course: one ontic reality (whatever it might in fact be) and many ontologies (each with its own proposed metaphysical laws) trying to accurately map it - often enough in manners that end up being contradictory to other ontologies.

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