As our only access to a possible outside us is through our senses, how can we prove that there is a world on the other side of these senses when we only know of this possible world through our senses? — RussellA

Surely we perceive the world via our senses doesn't necessarily mean that the world doesn't exist?
If it is due to limits and faults of human senses, then why does he have to doubt the existence of the world? Wouldn't it rather be fair to say our senses are imperfect, than trying to prove the objects exist outside us?

Not everyone believes that Kant succeeded. For example, George Dicker in his article Kant's Refutation of Idealism wrote: "I analyse Kant's Refutation of Idealism as he presents it in the Critique of Pure Reason and show that it is a failure". — RussellA

What is the reasons for George Dicker to claim that Kant's Refutation of Idealism has failed? Does it mean that Idealism prevails in CPR?

The knowledge as set out in his Theorem in B276 that objects exist in space outside us. — RussellA

I recall this part of CPR. It was about Refutation of Idealism.
What was Kan't intention for the proof?
Did he succeed in the Refutation?

IE, Kant proposes a proof in the Refutation of Idealism that we do have knowledge beyond our experiences. — RussellA

What type of knowledge would it be?

A question popped up in my head. Are the facts part of the physical world?

That mental impressions of number as cognitive math in abstraction are not categorically separate from their antecedent material objects making up the environment of the natural world is specifically what I mean when I say number is physical. — ucarr

But if something is physical, what properties does it have?

Numbers are universal? There’s a reason why teaching math to elementary students usually involves the use of material things that can be counted like, for example, wooden blocks. Without use of countable things named in the counting process, many elementary students, when shown equations on a blackboard, would see nothing but meaningless chalk scribbles. — ucarr

Is using the countable things only way teaching and learning the elementary maths?

If numbers were material and physical, then your numbers and mine would be different and contingent, which would make the universally necessary concepts and knowledge (Mathematics, Geometry etc) impossible.
— Corvus

You imply there are no logical relations between material things. The sum of my car parked on the street next to yours is no less calculable than one equation solved in our heads, respectively. — ucarr

This was not about material things. It just meant to say that you can perform math calculations and geometrical proof works without having to perceive the actual objects in front of you, which proves that numbers and geometrical axioms are A priori concepts, which are universally necessary truths.
They are universal in the way that if you calculate 5+7=12, and whoever in the world sees it will accept as a truth. You didn't need any objects to calculate the math with the numbers.

For example, if you had 5 cars parked in the front yard, and 7 cars at the back yard, then you don't need to personally visit the yard to count the cars whenever you want to know how many cars in total you own. You can do 5+7=12 in your head without seeing the cars or counting them, you get the answer. The reason you can do this is that because numbers are A priori concepts. Numbers are not material or physical.

I understand logic as an exacting type of continuity; it is continuity that adheres to strict rules of inference as they pertain to conjunction; disjunction; implication, mutual implication and the negation of these logical operations. — ucarr

What branch of Logic is this?

We’re they not, the fitness of memory would not affect abstract thought. This applies no less to higher orders of abstract thought because all its levels, ultimately, reduce to experience of the environment. — ucarr

What do you mean by this? Could you please rephrase it?

You’re uncoupling seeing the road from the road’s existence as a thing-in-itself. — ucarr

How do you uncouple seeing the road from the road's existence as a thing-in-itself? Does the road have a thing-in-itself? Or the thing-in-itself has the road? How were they coupled in what way?

Not sure if there was anyone witnessing the Big Bang
— Corvus
We did. It's not like it happened a finite distance away and the view of the bang has already passed us by. Of course the really early events are obscured by the opaque conditions back then. The window through which we look took a third of a million years or so to turn transparent. By that measure, nothing could 'see' the big bang since it was all obscured behind a blanket until then. — noAxioms

I don't recall seeing it at all. Or anyone who claims to have witnessed the Big Bang.
Could it happen again? Or is it still happening the now?

Nothing ever gets proved. I can go to grandma's house if I have a car, and the weather is acceptable, and if I draw breath. But technically I cannot prove any of those.
Point is, requiring 'proof' is going to far. Evidence of X,Y Z is probably enough for plausible time travel. Right now, that evidence is very negative. — noAxioms

There is a difference, when you are just keep talking to yourself making the "If" statements to yourself, and when you actually make philosophical propositions in public claiming that it is true or at least valid and sound.

Your interlocutors will request to prove your statements, if they sound unclear, invalid and unsound, so they can be rejected. Philosophical debates are about proving and disproving claims and statements as true, false or neither. And a statement cannot be both true and false. That wound be a contradiction.

The point is that unless it is your monologue or a pub talk, philosophical statements need to be proved and verified when not clear. If not, it could transform to a drama or comedy.

I am not sure what the physical clock measures.
— Corvus
It measures proper time, which is very defined in both interpretations of time. It doesn't measure the advancement of the present, or the rate of the flow of time. That sort of time is more abstract, and there is no empirical way to detect it, let alone measure it. So maybe we're talking past each other when I reference the sort of time that clocks measure, vs you referencing the latter. — noAxioms

It sounds like we are talking about different time here. What is "proper time" and "interpretation of time"?

This brings me back to the thought that animals may have as rich, or richer life experience than people. Even though they might not be self conscious of the fact etc. — Punshhh

:cool: :ok:

Memory and imagination, via the interweave of world and mind, play a game of give-and-take with environment. Ask any courtroom lawyer, or prosecutor, and he/she will tell you about the unrealiability of memory on the part of witnesses. Ask any senior citizen who’s just visited their childhood home after decades absent from it and they’ll tell you about seeing a world smaller than the one they remember. — ucarr

Saying memory can be unreliable therefore numbers are physical is a poor logic. Memory is an ability of the brain which is a biological organ. Of course its capacity can degrade with ageing, and other factors. It is like saying your eyesight got bad, and cannot see the road, therefore the road doesn't exist.

Imagine the ancient primeval times when the folks had lived in the caves, and hunting for survival. They had no numbers or languages, but they must have been fine with the living just going out roaming the forest looking for the food source. I am sure they had lived like that with no major problems for thousands of years. Numbers were discovered much later in human history, and it is just a mental concept.

It is strange why on earth you keep claiming that numbers are material and physical in the OP, and I was just trying to figure out your logic for the claim.

Numbers are concept and purely mental in its nature, and that is why they are universal. If you read Kant, you might have noticed that is what A priori concepts are about. Number works with material and physical objects, but it is not the same existence in nature.

If numbers were material and physical, then your numbers and mine would be different and contingent, which would make the universally necessary concepts and knowledge (Mathematics, Geometry etc) impossible.

Only if it is claimed that they necessarily must be. We're assuming them here to see if it makes time travel possible. It doesn't, but it does remove some of the issues and paradoxes. — noAxioms

Sure, I am not saying it is not allowed to have conjectures and hypothesis on time travel. My point was the claim that "If X, Y, Z, then time travel is possible." remains as a hypothesis until X, Y, Z had been proved as truths which complies to the objective facts in the actual world.

A physical clock measures something. Hard to deny the existence of something that can be measured.
You seem to get around this by defining time differently than, well than how physics defines it, which boils down to 'what a clock measures'. I agree that the coordinates we assign to time is pure abstraction. — noAxioms

I am not sure what the physical clock measures. But if it did, and if it is not something which is non conceptual time, then I would imagine it couldn't be time itself at all. It must have measured some particles going through changes into some other entities similar to the Nuclear fission process, which is the duration of the process. Would it be time itself? I believe not.

My point was more that if we counted from the Big Bang time might have some relevance beyond social time-keeping. If the year we're using is based on the very first change that ever occurred, its much more palatable, I think, to take it as 'something'. — AmadeusD

I heard that Japanese folks have their own time system counting from their monarch's coronation days. So they run their king's name and year 25 or 30 whatever, as their alternative year counting.

Not sure if there was anyone witnessing the Big Bang, and recorded the time and how it went through. Unless that is the case, many people would still take it as another mysticism.

In Chinese Lunar Calendar, it is still 2023 November or December at the moment. Their new year day would be sometime in February I think. The main point is, time is a civil contract.

Only one of these two statements is "in "if" form". — Luke

They seemed to be the concluding statements from your arguments.

Anyhow, do you deny that Kant was alive in 1776? — Luke

No I didn't deny anything about Kant or 1776. My point was that you need to prove your "If" statements are true to the objective facts, to make them into true statements.

Your arguments might be valid, sound and not contradictory in modal logical forms, but that doesn't mean that they are true in the actual world. Bear in mind that, whatever happens, they all happen in the actual world. Before the proofs, they just remain as your conjectures and another hypothesises, which are not adding much more to the OP question.

But this doesn't mean 'time doesn't exist'. It means are symbols for it are arbitrary. I'm not trying to say it does or doesn't exist - just that this doesn't go to that question i don't think. — AmadeusD

Time exists, but not in the way the would-be time travellers think. :D

It may be that it's actually the year 14,564,335,235 AT (all time). — AmadeusD

If you established your own country or created your own world, then you could run it with that, suppose.

Neither “concepts” nor “data,” divorced from physical reality, have any meaning or use. — ucarr

Concepts and data can exist without the physical objects purely in the minds. Do you need the physical reality and objects when you imagine, remember or think about something?

In my statement you don’t see any quotation marks, so that’s evidence I’m not quoting you. — ucarr

In that case, you have been reading my posts not properly. :D

If my argument for the similarity of the terms is correct, I don’t need to make any further changes to my above claim. — ucarr

The description of "number" in the OP sounded muddled, and seemed to be vague and incorrect, hence I was trying to clarify the concept with you.

I think you’re fundamentally wrong in your thinking number-signs hold the status of data before such linkage. — ucarr

No. I never said that. You are either misquoting me, or not reading my posts properly.
Before the linkage numbers are concepts. After the linkage, they become data.

Without the necessary cognitve_mnemonic linkage to the physics of number, — ucarr

What is the physics of number? I am trying to clarify the concepts, so that we can understand the points of the agenda better.

Apparently without intending to, you state my premise exactly. — ucarr

Your points were that numbers are material and physical. My point is that numbers are mental and conceptual.

Here you are expressing my premise again with a more complex model. Music, a complex interweave of numerical values of vibrating strings, exemplifies, more nobly, the physicality of number. — ucarr

Again as above, your points were that numbers are physical. My point is that numbers and data are conceptual. Until you link the numbers to the physical objects, they have no meanings. But once you have attached the numbers to the objects, they have meanings. Still my point is that numbers are concepts even after they are linked to the objects.

If I travel to 1776, then that was a time when Kant was alive. — Luke

It's possible that someone could invent the technology for time travel. — Luke

And another thing, forgot to add. Your concluding claims are all in "If" form. They are not propositions. They are hypothesises and conjectures themselves in "If~" form.

Your concluding statements would only be true, if and only if you proved the "If~" parts as Truths which complies with the objective facts. So far, I don't see any evidence or proof for your "If" statements having been proved either True or False, therefore they remain as groundless conjectures.

This seems inconsistent with the video you posted which describes time as “a measurement of the progression of events”. — Luke

Of course there are changes in the physical world and bodies. But that is not time. Time is measured quantities. There are durations and intervals, which is different from time. The claim that time is a mental concept, doesn't mean there is no physical and bodily changes.

Time is a conceptual product which is a mental product from observing the changes and intervals in the physical world such as the rising Sun every morning, the movement of stars, change of the seasons ... etc etc. It is not some physical entity.

You say year 2024 1990 ... but this is just some contingent contract of the human civilisations. It doesn't exist in the real world. It could be year 0 tomorrow if we all agreed.

Year AD1 was the year Christ was born. Do you believe in Christ's life? If not, then Year AD1 could have been any number. No one knows what year it should have been. We have no such thing as Time. It is an illusion.

One might equally demand to prove the existence of a single timeline before progressing further. I don’t see how this might work either way. I’m merely showing that time travel is hypothetically possible with a way to avoid the contradictions of the grandfather paradox and violations of the laws of causality. — Luke

From my own perspective, time doesn't exist. It is a mental concept. There is only "Now", no past and no future. What you call the past is your memory of the past now, and what you call future is your imagination.

Therefore I don't need to prove a single timeline or indeed anything at all. I would say, there is no such a thing as time. If you don't agree, prove that time exist, prove the past and future exist. If you cannot prove them, then all your points were just imagination. This would be my points to you. :D

Thanks for posting the video. — Luke

You are welcome.

However, I will argue, there must be two (or more) parallel timelines in order for time travel to make sense. — Luke

Sure. If you say, you are allowing the parallel timelines running in possible worlds, then the argument becomes logically tenable. But one might still demand to prove the existence of the parallel time lines, before progressing further.

However far-fetched this may seem, it does not violate causality and leads to no apparent contradictions. — Luke

It doesn't lead to apparent contradictions, but it doesn't make it true claims either. :)

You ask about the singer’s body in my little story. The measurement of his body is data, but that data has no meaning without his body to which it refers. — ucarr

But isn't the measurement data of the body, the property of the body, or a part of description of the body, rather than the body itself? For example, a person has a certain data associated with him such as DOB, name, sex, place of birth, height, weight etc etc. DOB is just one of the properties of the person, but it is not the person. There will be millions of other people with the same DOB, so DOB itself doesn't say anything about a person until it had been attached to a person.

It is not meaningful itself until it is attached to a person, but that is what the relation is about. You have measured and attached the measurement, hence related the numbers to the body and gave meaning to the numbers as the measurement of the body. Hence numbers are concepts, not physical or material?

What’s the meaning, which is to ask, “What’s the reality,” of musical notation on paper if it doesn’t refer to the singing man, or even to the leaves rustling in the breeze? — ucarr

Again the musical notation on the paper has no meaning until it had been performed by the singer. The notation itself is not the music, but an instruction how the singer must perform the music? Therefore, should we not class it as a concept too? Once the singer masters how to sing the song according to the instruction, the singer no longer needs the instruction. He throws it away in the bin, and just sings away as he pleases and wants on his own style and moods. He would still follow the instruction for the singing, from his memory, not from the notation on the paper.

If an idea means to have mental images from the sense perceptions such as visual perceptions and memories, then the animals must have ideas just like humans do. Because they appear to be able to recognise many things and perform leisurely and survival tasks in intelligible ways based on their visual perceptions and memories.

But if an idea means the semantic elements, then animals definitely lack the possession of the mental concepts and abstract ideas based on linguistic expressions.

If we agreed on the claim that animals are supposed to be able to have ideas based on the sense perceptions and memories, then still, it is not clear if they would have the critical, analytic and abstract thinkings on the metaphysical topics such as the world, God, souls, immortality and death. I am prone to think they don't appear to, and it might not be a bad thing for leading a happier and simpler life, compared to humans tending to be worrying, thinking, analysing, criticising, doubting and contemplating about these issues due the possession of the extra layer of intelligence.

What size and weight, what shape and color, his tenor voice? The width of his nostrils, the length of his lungs, the breath of his chords, is it? — ucarr

Isn't the measurement of his body just a form of data? Data is not material or physical. Is it?

These numbers are sizes of music and song, but one man is he. Oh, glee of sweet nighters. — ucarr

Do music and song have size? Is it a metaphor or what?

This short video summaries my points on time travel.

This is what I mean. Corvus seems to assume presentism with this statement. The whole notion of time travel seems to assume otherwise, that there are 'other times' available as valid destinations. — noAxioms

If you insist that you can travel into the past or future in your imagination, yeah I would say it might be imaginable within your imagination. I was only pointing out the impossibility of time travel in the physical world.

Funny that you will nevertheless travel to tomorrow. I plan to see you there.
People talk about time dilation being time travel. It isn't any different than doing the same thing sitting still. You get to 'the future' either way, assuming you live long enough to get to the target destination. — noAxioms

Strictly speaking there is no tomorrow in reality. What you call tomorrow is in your imagination as a concept or idea. There is only "Now" for the whole universe and its members. :) So you might say, we are travelling into tomorrow, but in actuality you are awaiting for another "Now" which will be in next 24 hrs of duration.

If you’re a Kantian or similar about time. Not everyone is. Beside this, time as a concept describes a pattern which actual does obtain among material and bodies. Just move through the pattern of materials. — AmadeusD

Yes, my view of time is similar to Kantian time.  It is a concept in mind.  Time doesn't exist in the physical world like space does.

Unless you deny the external world entirely, changes exist. Choose your “point in time” based on the “previous state of affairs” you’re after. No need for dates - but would require a more god-like knowledge of history — AmadeusD

Do you claim that change is the same thing as time?  No, one can deny the existence of time without denying the existence of the world.  They are totally different things altogether.  The world exists physically, but time exists in mind.

I don't think it is me who has difficulties in understanding the issue.  It was Luke who had to prove that his statements were logical.  I had clear arguments against them. 
So what is your own definition of time, and time travel? Can you travel in time physically, or is it in some other way?

Time is a concept in mind. Travel means physical motion describing going from physical location A to B. How do you travel in the concept to another physical location, unless travel means something else such as an extremely odd imagination? Or time means some other object such as a town or city called Time?

Absolute nonsense. Goodbye. — Luke

That's a poor argument and conclusion. Good day. :)
I will reconsider your statement for its truth, if you come back with the clarifications for all the mysterious terms you used in it.

Your statement is a typical case for a logical form itself cannot verify the truth / falsity of statements. You must investigate the contents i.e. concepts and ideas in the statements or propositions for its clarity and soundness for the fitness as qualifying the elements for legitimate truth bearers.

If you are using unclear, mysterious or false terms or ideas in statements or propositions, it should be pointed out, and the whole claim must be classed as invalid, unsound or false before checking out the logical forms or structures.

You said it wasn't clear what the statement or its terms mean. How do you know it's not true if you don't know what it means? — Luke

I knew the negation of the statement was clearer, and it gave the ground for the truth, which entailed the falsity of your statement.

Non sequitur. If it's an unclear statement, how does it follow that it's not true? — Luke

It is not true, because its negation is true.

Very poor. You've offered zero support for your assertion that time travel "is an impossibility from the reality of 2024". — Luke

Support is not our goal of argument. The goal of the argument is finding out which statement is true. It seems clear that yours is not true.

P.S. : You have not managed to clarify any of the unclear terms in your statement, which are the base of the invalidity, and entailing the ground for its falsity.

I already answered that. It's possible that someone could invent the technology for time travel.

You said it was impossible and that my premise was false. The onus is on you to explain why it's impossible. — Luke

I thought it was obvious. Your statement has too many unclear terms. When it says someone could invent, who is someone? Does he exist in the real world? What is his name? Where is he from? What does he do?

The technology, which technology is it? What is the technology based on? How does it work?

And time travel? What do you mean by time travel? Does time exist? In what form does it exist? Travel? what do you mean by travel? Are you physically going somewhere? Where is the destination?

So, you statement is made up with the terms which doesn't have clear meanings. Therefore your statement is not true, and the negation of the statement is true. Because the negation of the statement is true, your statement is false. How is that? :smile:

For you to refute my argument, you must clarify all the unclear terms in your statement with concrete clarity in meanings, and we can start again thereat.

Since your question asks about the “object” you can’t count, a word single in number, haven’t you already counted it? — ucarr

My original question was about number, not object. But your reply was about object, and I was asking about them too. Why do you want to count object which you can't count? And " a word single in number,"??? - what does it mean?

My original question was, if number is material and physical (as claimed by the OP), then what measurements in size and weights does it have? And what shape and colour does number have for its physical and material existence?

Why do you say it's impossible? It is possible that someone will invent the technology for time travel in 2024. — Luke

In what sense is it possible, or under what ground is it possible?

Name a material object with any of the following: length, weight, form or color that you can’t count. If you find all such material objects are countable, you have your answer. — ucarr

Could you provide some examples of such material objects? How do you find countable objects from the object you can't count?

"All the world's a stage, and all the men and women merely players. They have their exits and their entrances; And one man in his time plays many parts."
As You Like It, Act 2, Scene 7, Shakespeare

Not to beat a dead horse, as he has been banned, but what did he even mean by that? — Lionino

Shakespeare has been dead for almost 400 years.

boagie has been banned for low quality and toxicity. — Jamal

Understandable and reasonable decision. There is no place for toxicity, derogatory languages or the swearing directed towards the individuals in Philosophy. We can disagree with, demand evidence and proofs, and reject the opinions, views and points of others.

But I understand that, still all of us are expected to have respect, the good spirits and basic manners towards the fellow members whoever they are at all times.

If I travel to 1776, then that was a time when Kant was alive. — Luke

Your premise "If I travel to 1776" is an impossibility from the reality of 2024, and therefore it is false. Your conclusion is true in that 1776 was the time Kant was alive.

Even if your conclusion was true, but because your conclusion was drawn from the false premise, your proposition is invalid.

In essence I’m saying that instinctive behaviour is very much thought, thinking. — Punshhh

Yes, I agree with all of your points.

How would these people who are explaining away thinking describe what a cat, or for that matter, a spider spinning a web is doing? — Punshhh

In the case of cats and dogs, and monkeys, they seem to show the intelligent activities in their daily lives.  They definitely have the clear evidence of possessing some level of intelligence, and their reasonings are mostly based on their sense perceptions and memories.  They also seem to understand human words when spoken to them although they cannot make linguistic expressions uttering words and sentences.

And even in the case of the spiders putting up their webs to trap their preys for their survival, it looks in most cases it has been done under the well thought out plans.  They tend to put up the webs in the good locations where it is dark, dingy and corner of the attics or ceilings where it is likely to attract their prey more than the implausible places such as in the middle of the roads, on the dining tables in the kitchens, or in front of the shower heads etc.  

But then we wonder, there are many more insects, mammals, fishes, planktons and even the plants and trees ... etc all seem to be selecting their habitable locations reasonably.  Trees tend to grow more in mass in the forests with the warmth of more sunlights and rainfalls combined with the rich soil bases.

The ants, bees and squids, octopuses, grasses, weeds, roses, they all seem to be selecting the places better for their survivals, and seem to be doing the right things looking for their food and making their shelters under the ground, soils and seabeds as necessary for their best survival chances.  Does that mean they must be all thinking and reasoning, abstracting and having ideas for their plans, and reflecting their pasts?  What do you think?