No, you didn't. You merely asserted: "The PSA statement (that there is a step that reaches the goal) directly violates the premise that any given step gets only halfway to the goal." There is no direct violation.Or the PSA is correct, and the goal can't be met.
— Relativist
I showed that for a supertask, the PSA is not correct. So no, this cannot be for a supertask. — noAxioms
Fair enough, I misstated it. The process does not continue forever, however there is no end to the process.If the process continues forever, by definition it isn't a supertask. — noAxioms
My point was that the kinematic stair-stepping process has a temporal element that is not reflected in a number line.Points on a number line exist concurrently (in effect).
— Relativist
I don't know what is meant by this. 'Concurrently' means 'at the same time' and there isn't time defined for a number line.
A number line seems to be a set of ordered points represented by a visual line. It can be defined otherwise, but functionally that seems sufficient. It being a visual aid, it seems physical, but a reference to the simultaneity of the positions along the line seems irrelevant to the concept. — noAxioms
Or the PSA is correct, and the goal can't be met.The PSA statement (that there is a step that reaches the goal) directly violates the premise that any given step gets only halfway to the goal. — noAxioms
I'm not merely asserting it. You have to agree that a final step is necessary for completion when there are finitely many steps. Why would it matter if the number of steps is infinite?Relativist: "Simply denying a final step is necessary doesn't make it so."
Simply asserting that such a step is necessary doesn't make it so — noAxioms
Here's how: the infinity is manifested as a never-ending kinetic process.Relativist: "you have to explain why it's not necessary for a kinetic task to require a final step in order to be completed."
I don't know how the task being 'kinetic' changes the argument. — noAxioms
Yes, the PSA entails taking a final step. We agree infinity is not a number, so there is no final step.Doing successive steps does not get you past the tortoise unless the passing of the tortoise is done by one of the steps. That's the same as suggesting a final step, which suggests that infinity is a number. — noAxioms
Show the PSA is false.I cannot buy into that PSA statement.
Why? The claim is indeed justified by the necessity of a final step for completion. Simply denying a final step is necessary doesn't make it so - you have to explain why it's not necessary for a kinetic task to require a final step in order to be completed.But I'm making the stronger claim that it is logically impossible.
— Relativist
I'm trying to get a justification of that claim without the addition of the necessity of a final step, which would by definition be contradictory. — noAxioms
In the case of Achilles, we know that the task can be completed, but it is presented to us in a form in which it cannot be completed. I mean that we know that Achilles will pass the tortoise and even calculate when with simple arithmetic (no infinities required). — Ludwig V
We can assign those numbers as we take each step. That's counting, and it's perfectly meaningful.Countably infinite means that any step can be assigned a number. It does not in any way mean that there is a meaningful count of steps. — noAxioms
OK, but speed of light limitations put a physical limit on how fast the stairs can be descended, so that it eventually becomes physically impossible to descend a step in the prescribed period of time. The minimum size limitation also relates to a physical impossibility. But I'm making the stronger claim that it is logically impossible.Physical (fixed size) stairs are of infinite length, and such a distance cannot be traversed in finite time. If the stairs get smaller as we go, then we get into the physical problem of matter being discreet, not continuous. Hence the steps have a minimum size. That's what I mean about physical stairs not qualifying as a supertask. — noAxioms
The entire exercise is abstract, but the scenario is written in terms of the kinematic (not abstract) process of descending stairs: each step is a motion, taking place in a finite amount of time.Relativist:"The mathematical series completes, but this is an abstract, mathematical completion. The kinetic activity of descending the stairs does not complete."
Again, the stairs is utterly abstract. There's no kinematics to it. — noAxioms
Taking a single step is an act. The acts are performed in a sequence (from step n to step n+1). The term (sequence) is not referring to the entire collection. The task is to reach the bottom of the stairs (as stated in the description in the first post of this thread). Perhaps you can already see that it's trivial: it's actually impossible to reach the bottom of the stairs, since there is no bottom to a staircase with infinitely many stairs.PSA:The performance of a sequence of successive acts does not complete a particular task unless it is completed by the performance of one of the acts in the sequence.
I cannot parse this. What is an 'act' that is distinct from a 'task'? The word 'sequence' seems to refer to the entire collection.
A 'task' (what, one of the steps??) is not completed by a performance unless 'it' (what, the performance?, the task?) is completed I cannot follow it at all. — noAxioms
Correct.Am I right to think that you are not saying that all the stairs can be counted, even though any stair could be included in a counting sequence? — Ludwig V
I think it's because they are interesting puzzles, and because they help teach certain concepts.That's true. What puzzles me is why they are not dismissed out of hand. — Ludwig V
Yes- that's a better way to describe it.Wouldn't it be more accurate to say that descriptions of the supertasks are the source of the illusion that there could be a mapping of that mathematical series into the actual kinematic world? — Ludwig V
The allure of supertasks is the illusion of being able to complete an infinite process in a finite amount of time. I'm not sure there's anything comparable.More than that, surely, there can be a mapping of some mathematical series into the actual kinematic world. Perhaps some similarity between those series is what creates the illusion?
This is a thread about the religion Flawlessism. If you actually knew that religion you would know that your argument has no basis because of what I'm referencing to. If you don't know what Flawlessism is then don't comment. — Echogem222
My point is that the stairs are countably infinite. Consequently, they COULD be counted, if we were traversing them.I had not mentioned a completion of a count. The supertask is to complete all steps, not to count them, and not to complete a specific step that is nonexistent. — noAxioms
Yes, the sequence of defined temporal points (1/2, 1/4, 1/8...) is a series, but the mathematics that identifies the limit does not take into account the kinematics of the task. Supertasks describe a conceptual mapping of the abstract mathematical series into the actual, kinematic world - regardless of whether or not you wished to consider it.The series (say the time needed to complete all tasks) converges. The count does not.
It fits this definition:The physical process of descending stairs is not a supertask. — noAxioms
The goal of removing all the marbles will therefore never be met if there are at least 2 green marbles, and it will rarely met even if there is only 1. How does this relate to a supertask that allegedly completes?Cheap example: You have a bag with a modest quantity of red, blue and yellow marbles in it. The goal is to remove them all. The task is deemed to be complete when the green marble is removed. Such a task cannot be completed by that definition of complete. — noAxioms
The article discusses the issue:I notice the SEP article correctly doesn't claim that the last step is taken. — noAxioms
Yes, it's a cop-out because it ignores the kinematic process. Stating this in terms of the PSA gives you something specific to address, if you want to not cop out.Relativist: "Your preferred perspective ignores this - or pretends there can't be a final step because that introduces a contradiction."
There being a final step leads directly to contradiction, and you say I'm copping out by pretending there isn't a final step? — noAxioms
I agree we can't treat infinity as a number, and haven't suggested you should. But for the supertask to be meaningful, you have to identify where infinity fits in the kinetic task description. I'm saying it entails a never-ending sequence of tasks. Identifying the limit doesn't make this disappear.Relativist: "For the scenario to be coherent, BOTH view of completeness have to be true."
I cannot accept this assertion. I cannot accept a view of completeness that treats infinity as a specific number. — noAxioms
I think you're referring to the limit:There are some number systems that define division by zero as a/0=∞. — Michael
Please clarify what you mean. Are opinions not beliefs?Rather, opinions are propositions that are not truth-functional. — Lionino
How do we decide what is fact and what is opinion? — Truth Seeker
The premise that the universe "popped into" existence is incoherent. It implies there existed something, into which the universe popped.Things don't pop up for no reason, in fact, that is an assertion that implies a cause(in this case, 'no reason'). Given this, it is wiser to assert that the universe came into existence by some manifestation in, per se, a multiverse, than it is to park randomly on the conjecture it just popped up for no reason — Barkon
Yes- and that's because the role of infinity in the task. The task entails a sequence of events, so the infinity can only mean an infinite chain of events - one after another without end.the process of counting steps is not completable
— Relativist
Are you suggesting that supertasks cannot be completed? — keystone
Wrong. The statement (the completion of a consecutive series of physical steps entails a final step) is necessarily true. When we consider this statement in conjunction with a statement about the series being "complete" (in terms of convergence) we introduce a contradiction. This is the point! These statements cannot both be true, but both are entailed by the scenario.if a physical process ends, there has to be a final step.
— Relativist
This is equivalent to asserting that 'infinity' is the largest integer. — noAxioms
The SEP article says:But as Thomson (1954) and Earman and Norton (1996) have pointed out, there is a sense in which this objection equivocates on two different meanings of the word “complete.” On the one hand “complete” can refer to the execution of a final action. This sense of completion does not occur in Zeno’s Dichotomy, since for every step in the task there is another step that happens later. On the other hand, “complete” can refer to carrying out every step in the task, which certainly does occur in Zeno’s Dichotomy."
The definition you appear to be using is the former, which is why Michael's one-digit counter doesn't have a defined output after the minute expires. — noAxioms
I agree with this, but this simply ignores the implication of the physical process of step-counting. For the scenario to be coherent, BOTH view of completeness have to be true. But they aren't - so the scenario is actually incoherent.I've been using Zeno's definition of complete: That every step has been taken. Given that definition, the supertask can be completed. — noAxioms
Right! It's not the sequence described in the scenario! There is a background temporal sequence, as the clock ticks, that reaches 1, but we aren't mapping the step counting to the ticks of the clock. The step-counting sequence occurs only at points of time <1. In real analysis, this is called a "right open interval" (i.e.it's open on the right= the endpoint is not included in the interval). 1 is the endpoint, but not included within this interval.As I have been explaining in this thread, you can conceptually adjoin the limit of a sequence to the sequence, as in 1/2, 3/4, 7/8, ..., 1. This is a perfectly valid mathematical idea. This is a representation of the ordinal ω+1
+
1
. In this case, 1 is indeed the "last term," although to be fair, you can no longer call this a sequence, since a sequence by definition is order-isomorphic to the natural numbers. — fishfry
The limit of the series is "reached" only in the sense that we can reach a mathematical answer. The physical process of sequentially counting steps, doesn't "reach" anything other than increasingly higher natural numbers. Deriving the limit just means we've identified where the sequential process leads. In this case, we've derived that the limit is infinity- but what does infinity correspond to in the scenario? The meaning is entailed by the fact there are infinitely many natural numbers, so it means the process continues without end. It can mean nothing else.By definition, a limit is not reached, it is approached.
— Relativist
That is sadly a misunderstanding very common among calculus students. So lot of smart people, physicists and engineers and other scientists, have this belief.
In fact a limit IS reached. A limit is exact, it's not merely approached or approximated. It is literally reached.
It's not reached by a single step. Rather, it's reached by the limiting process itself. — fishfry
The lesson is that the defined supertask (the fictional, physical process) is logically impossible,
— Relativist
The lamp and staircase scenarios are physically impossible. What law of logic makes them logically impossible? — fishfry
I'm asserting that an infinite process is necessarily never completed - by definition.the process of counting steps is not completable
— Relativist
Are you suggesting that supertasks cannot be completed? — keystone
The scenario describes a fictional, physical process. The lesson is that the defined supertask (the fictional, physical process) is logically impossible, but this isn't apparrent when considering only the mathematical mapping.There is no physical process. — fishfry
That's because the physical steps map to an infinite series in an interval with an open boundary. One can't simply declare there's no final step because the mapping implies there isn't. The taking of steps is a repetitive physical process, and if a physical process ends, there has to be a final step.Certainly the relationship between time (independent of human control) and physical steps taken over a period of time has ended. — jgill
Consider a devotee of Infowars, who routinely accepts conspiracy theories. Aren't you suggesting they should trust their opinions?We of course have the ability to develop our skills of thinking things through, analyzing our opinions and assumptions, and considering other perspectives. But there is a difference between ensuring what you say is correct, and how you conduct yourself in and after saying it. So to say you should “not trust your mind” (yourself)—as I, and Emerson, argue against above—is perhaps different than saying you should not trust the opinions you have or inherited. — Antony Nickles
Mathematically, this sequence as a limit of 1.
The sequence never "reaches" 1; nor is there a last step. Neither of these statements is controversial once you understand what a limit is. Sadly, most people have never taken calculus; and most students who take calculus never really learn what a limit is — fishfry
You should NOT trust your mind, but you can gain trust in certain beliefs by applying critical thinking: seek out contrary opinions, test your beliefs through discussion with others (like on this forum), attempt to mitigate confirmation bias by trying to identify objective reasons to support or deny some presumption you may have. Learn at least some basics of epistemology (including the limits of each technique).Everyone can be rash, everyone can be stupid, misinformed or otherwise malpracticing adequate reason.
My question is how does one know when that is the case - ie they're chatting sh*t. And to the contrary, when they really do know what they're talking about.
What is the litmus test in the realm of discourse with others which may be either just as misinformed or very much astute and correct? — Benj96
The paradox is this:I don't even understand what the supposed paradox is. — fishfry
Indeed, the stipulated elapse of a minute implies all the steps would have been traversed, but that implication is contradicted by the fact that the process of counting steps is not completable. The presence of this contradiction implies there's something wrong with the scenario.We can also map the steps to the elapsed time (1 → 0.5, 2 → 0.75, 3 → 0.875, etc.). If we conclude that a full minute has elapsed, doesn't this imply that he has traversed all the steps? — keystone
Same as above: it's a logical relation (atemporal) that does not account for the stepwise process that unfolds in sequence (temporally).Analogously, a limit entails an abstract operation applying to a mathematical series and shouldn't be conflated with a consecutive process.
— Relativist
Why not?
I disagree. It's absurd because the counter progresses through natural numbers, and can never reach a final one. Infinity isn't a natural number. In the context of a temporal counting process, infinity = an unending process, not something that is reached (and not a number).If time is infinitely divisible, the counter would go up to infinity. Not a conclusion that many of us may like, but there doesn't seem to be anything logically absurd with it. — Lionino
Imagine a universe where not only is everything possible, but that all possibilities must be fulfilled before its natural conclusion.
How might such a universe look? How might you describe it? How would it begin and end? How would it evolve and unfold? What would concepts such as "paradox", "contradiction", "logic", "irrationality", "belief" and "fact" mean in such a universe? How might all these dynamics interact? — Benj96
There's nothing contradictory with the EXISTENCE of an actual infinite, but it's not accepted that an infinity can be traversed in a supertask. In the case of the staircase, there actually is no last step - so it was correct to say the staircase was "endless".That would be analogous to saying the largest natural number can be reached by counting. This same objection has been raised in regard to the Zeno walk (see this SEP article).What you seem to overlook is that I'm beginning with a premise widely accepted within the mathematical community: the existence of actually infinite objects (like these infinite stairs or the set, N) and the completion of actually infinite operations (such as traversing the stairs or calculating the sum of an infinite series). If you do not accept the concepts of infinite sets or supertasks, then this paradox is not aimed at you. If you claim that an old woman is 2 years old, then you're not basing your argument on any widely accepted concepts of age. — keystone
There is a contradiction in the stated scenario: there's an END to the ENDLESS staircase. Better to ask where he is after a minute.Despite the staircase being endless, he reached the bottom of it in just a minute. — keystone
Absolutely. For example: what is the ontological bedrock of physical reality? No matter how deeply we explore, we can't know we've reached rock bottom.Are there things in the physical universe that we can never find out? — Vera Mont
I watched the video, and read the Brookings report. The person in the video grossly misrepresents the report. Brookings does not state a plan, it lists options - and identifies potential negative and positive consequences of each. The author's premise is that there is some secret plan to go to war with Iran, and he interprets points in the Brookings document to in light of this premise. The fact that certain events have unfolded with some of the anticipated consequences is a testament to Brookings' analysis, not an implication that one particularly nefarious path has been chosen by the US, among all the permutations of paths outlined by Brookings.the truth is that they have been planning for such a war since at least 2009. — Tzeentch