It seems to me that a better experiment could have been performed to show if babies are aware of quantities. It seems to me that we would need to know how the baby forms categories, as in there being a quantity of balls or a quantity of the color red or blue. — Harry Hindu

I was just reporting my understanding of how the tests were performed. If you'd like more detail, I'm sure it's published somewhere.

You’re going to go get your keys, you know beforehand and therefore a priori the keys are on the table because you put them there, but you have yet the experience of picking them up from the table, so you don’t yet have the knowledge a posteriori that in fact they are there. — Mww

You make it sound like everything I know is a priori. If I have to wait to know they are on the table till I pick them up, then they aren't even on the table anymore. Then they were on the table. Do I actually have to be standing there looking at something before it is a posteriori?

So I know the keys are on the table because I remember leaving them there. Or do I know they are there because that's where I always put them. Are either or both of those a priori?

In Kant but missing from Hume and Enlightenment empiricists in general, on the other hand....and for whatever it’s worth....is the notion of “pure” a priori knowledge, that in which there is no element of experience whatsoever, and these are principles, most obvious in geometry and propositional logic. The beginning of a very complex story indeed, and to some hardly worth the effort and consternation, considering the result. — Mww

I hadn't heard the term "pure" in this context before. How are pure and impure different from synthetic and analytic? What you are calling pure a priori sounds like analytic.

It doesn't make sense to call knowledge a priori if it's dependent on knowledge based on experience. I don't see how that is different from what is called a posteriori knowledge. — T Clark

The distinction is between what can be known only contingently on the basis of ongoing events and what can be known as necessary based on reflection about the nature of all our experience. So I know a priori that I won't know whether it will rain today until it does or the day is over, and I know a priori that rain can be more or less intense and comes in different forms, that it will have a certain duration and that like all things in nature it is never exactly the same from one event to the next..

So I know the keys are on the table because I remember leaving them there. — T Clark

Technically here, what you know a priori is in the remembering of what you did, so the conventional iteration would be, I know I left them there. Here is where the element of experience makes your a priori knowledge regarding the keys, “impure”. In effect, your knowledge at this time, is the memory of putting the keys on the table, given from the original experience, but not the experience itself. It is knowledge of the same object, but at different times. This was Kant’s refutation of Hume, nutshell version.

Another way to look at it: you know the keys were on the table because you put them there, that activity is in itself an experience, giving a one-to-one correspondence between knowledge and experience. Given that procedural necessity, you can not know the keys are still on the table, because you don’t have the experience of perceiving them as being there. But the initial knowledge doesn’t just disappear, so it must be accounted for....sorta like entropy, donchaknow.....so you are entitled to say your knowledge is now of the memory of the prior experience, which you certainly wouldn’t deny. You know the memory is just as certain as the initial activity, the former is properly intuition, the latter is experience.
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What you are calling pure a priori sounds like analytic. — T Clark

All analytic propositions/judgements/principles are pure a priori, but not all pure a priori propositions/judgements/principles are analytic. The distinction resides in the relation of the concept in the predicate to the concept in the subject of such proposition/judgement/principle constructions. A further distinction is that analytic constructions are tautologies, they are true necessarily, hence require no empirical proof. Synthetic constructions, on the other hand, are not necessarily true, hence require experience for such possible proofs.

As I said....for whatever that’s worth.

As I said....for whatever that’s worth. — Mww

I'm lost. Not your fault. I'll blame Kant.

As I said....for whatever that’s worth. — Mww

One more thing - the way you are defining "a priori" is not the way it is normally used here on the forum. Again - not your fault.

I think there's been a major distraction here. Kant wasn't concerned with whether we had hard wired empirical data in our brains, like if we have an innate fear of falling and instinctively cover our heads when we fall, or if infants instinctively turn their head to locate the nipple when the cheek is stroked.

His concern was whether there were a priori synthetic judgments, meaning could some new fact be known about the world through reason alone. That is, unlike knowing that bachelors are unmarried (analytic), when we determine the length of the hypotenuse from the length of the other sides of the right triangle, we now have new knowledge prior to experience (synthetic).

As I said, the sum of two and two is true in this universe. Whether it is not true somewhere else is irrelevant. — Harry Hindu

Philosophy is irrelevant then, so I disagree. It actually matters a lot to me. OK, it being true in this universe is enough for a priori knowledge, but I’m interested in it being objectively true.

Something else would be true in the other universe, like 2+2≠ 4

That would be a disappointment, but barring an example, I suspect otherwise.

:brow: Seriously? You really think that there was ever a chance that you could have been a bug?

You misunderstood what I wrote then. I was trying to illustrate why the ‘why am I me’ question is baffling only if dualism is assumed.

Anyway, the 'I' in that question is the self again, and if you deny the existence of it, the improbability goes away. — noAxioms

I said I (the self) could no more be a bug than it could be me. I denied its existence. There is nothing ‘being’ me.
The point of the example was to illustrate that everybody knows what Paul Simon meant by those lyrics. People have a dualistic instinct, a lie that is pretty much impossible to disbelieve.
Without it, the lyrics don’t make any sense since X is X (a tautology) and cannot be Y. But it makes sense to suggest the experiencer of X were to experience Y instead.

Yes, given dualism, there are a lot more non-human things to be (bugs being one example) and thus odds of winning the ‘human lottery’ are suspiciously low. Some get out of this via anthropocentric assertions, that humans are special this way. Questioning the lie is often not an option.

Your Paul Simon quote isn't saying anything other than "I wish that I could be a different I".

Even that makes no sense. How can say a cat be a dog? A thing is what it is and cannot meaningfully be something else.

Why am I me? Because a unique arrangement of half of my mother's genes and a unique arrangement of half of my father's genes were fused together to make the unique me. We are all unique outcomes of different halves of our mother's and father's genes.

That’s why your physical appearance is what it is, which wasn’t the question. The question asks why you look out of Harry’s eyes and not the eyes of another. The question makes no sense outside of a dualistic context since under monism it is tautological that a creature looks out of its own eyes (exceptions to robots with bluetooth).

I think there's been a major distraction here. Kant wasn't concerned with whether we had hard wired empirical data in our brains, like if we have an innate fear of falling and instinctively cover our heads when we fall, or if infants instinctively turn their head to locate the nipple when the cheek is stroked. — Hanover

This thread was never intended to be about Kant, although what he wrote is relevant to the discussion. As it says in the OP, the subject is "What do we know without knowing anything? Without justification... This type of knowledge is described many ways, among them a priori, self-evident, intuitive, obvious, and common sense." So a priori knowledge is part of it, but what babies know is also part. The discussion has focused on Kant quite a bit, and I'm fine with that. I've learned a lot, although I'm still confused by the terminology - synthetic vs. analytic; pure vs. impure.

pure vs. impure. — T Clark

The pure/impure is Kantian terminology specifically, meant to show the distinctions in what can be considered a priori. The thing with the keys shows there is a kind of a priori in common usage but hardly recognized as such, but it is the other kind of much more importance, that being, absent any element of experience whatsoever, that is, pure, which if not from experience, must the be from reason itself. Your list of a priori conditions on pg 1 are both kinds, but without the distinction of which is which. Conventionally speaking, that is sufficient, insofar as conventionally no one cares, but both scientifically and metaphysically speaking, it is very far from it. And, of course, you did ask a metaphysical question after all, so......just thought I’d weigh in. Or.....wade in, more like it.

Anyway.....of much more importance is the analytic/synthetic distinction, a priori being given. There are no analytic statements that are not a priori, which leaves synthetic statements. The whole scheme evolved from Enlightenment academia, as to whether or not there is any such thing as a synthetic a priori condition, and if there is, what is it for, what would it do, what can we get out of it. Believe it or not, the long and the short of it is.....and you know....for what it’s worth....., the question was asked about such things, because the question was first asked.....how is mathematics possible? Which is hardly as silly as it seems, insofar as an entire paradigm shift from Renaissance intelligencia in the ways and means of human knowledge, still in force to this day, resulted from such a simple question. Einstein, it goes without saying, did the same thing, except for the natural scientist rather than the philosopher.

One of Kant’s many claims to fame is the logical proof for them, and from it, the absolute necessity for what they do. Since, of course, there have been refutations of both the proof and the use, on the one hand, and deductions of them under other premises on the other, but nevertheless, the first and the most readily understandable iterations of them, are his.
————

My preference would be that we focus on the general question of what can we know without empirical knowledge — T Clark

Do you think there has been a satisfactory answer to that?

The pure/impure is Kantian terminology specifically, meant to show the distinctions in what can be considered a priori — Mww

So Kant's pure reason is a priori reason? Are we born with reason? Can we find it somewhere hidden in a cave? Between the lines maybe? How we know it's not declared a priori after it's introduction?

I was just reporting my understanding of how the tests were performed. If you'd like more detail, I'm sure it's published somewhere. — T Clark

It seems to me that your understanding isn't an understanding at all if you are unable to communicate it without contradicting yourself. It seems as if you are the one that needs to search for the publications and read them if you want to make an argument against anything that I've said (like experience is quantifiable).

Philosophy is irrelevant then, so I disagree. It actually matters a lot to me. OK, it being true in this universe is enough for a priori knowledge, but I’m interested in it being objectively true. — noAxioms

That would be a disappointment, but barring an example, I suspect otherwise. — noAxioms

If there is more than one universe then are we not already acknowledging that there are a number of universes, and that there might be different universes where there are two universes in which 2+4=4 and 2 in which 2+2=7, but there are 2+2=4 total universes?

Would it make any sense at all to say that we can add 2 universes to 2 other universes to get 4 universes yet 2+2 does not equal 4 in a certain universe? So it seems that 2+2=4 isn't dependent on the property of some particular universe, but is dependent on there being more than one of anything (including all universes). Even if there are only two universes, then 1+1=2 would be true regardless of what is true in either universe.

You misunderstood what I wrote then. I was trying to illustrate why the ‘why am I me’ question is baffling only if dualism is assumed. — noAxioms

Because you are assuming that there is an I that is separate from the individual (dualism). The question, "why am I me?" is a meaningless question (many philosophical questions are) if you understand that you are the result of a causal chain of events, and that if there was a different chain of events, it would not be that you would be some one else, rather you wouldn't exist at all.

I said I (the self) could no more be a bug than it could be me. I denied its existence. There is nothing ‘being’ me.
The point of the example was to illustrate that everybody knows what Paul Simon meant by those lyrics. People have a dualistic instinct, a lie that is pretty much impossible to disbelieve.
Without it, the lyrics don’t make any sense since X is X (a tautology) and cannot be Y. But it makes sense to suggest the experiencer of X were to experience Y instead. — noAxioms

Dualism is not an instinct. Babies are born solipsists. Most animals are solipsists. Solipsism is instinctual. After a period of mental development, babies become realists in realizing object permanence (that objects continue to exist even when not being observed or thought about).

Dualism is indoctrinated at an early age with the introduction of religion (soul vs body). The notion that you can exist independently of your body is a delusion created as way to deal with the knowledge of your death.

Yes, given dualism, there are a lot more non-human things to be (bugs being one example) and thus odds of winning the ‘human lottery’ are suspiciously low. Some get out of this via anthropocentric assertions, that humans are special this way. Questioning the lie is often not an option. — noAxioms

There is no lottery. There is no luck. Things happen for a reason (prior causes or pre-existing conditions). If something else happened instead then you wouldn't be here asking these questions. Someone else would be.

Even that makes no sense. How can say a cat be a dog? A thing is what it is and cannot meaningfully be something else. — noAxioms

That was my point. Either way you put the question, it's a silly question given that we know that you are the outcome of a particular sex act between two specific people and the subsequent development (life experiences) without which you wouldn't exist at all, not that you'd be something else - as if that were ever possible. It isn't.

That’s why your physical appearance is what it is, which wasn’t the question. The question asks why you look out of Harry’s eyes and not the eyes of another. The question makes no sense outside of a dualistic context since under monism it is tautological that a creature looks out of its own eyes (exceptions to robots with bluetooth). — noAxioms

Well, yes, which is why I said you need to abandon dualism if you want to avoid asking silly questions that simply don't take into account what we know today in modern times when religion and it's dualistic thinking is on the decline and replaced with scientific theories of biology, genetics and evolution.

The pure/impure is Kantian terminology specifically, meant to show the distinctions in what can be considered a priori. The thing with the keys shows there is a kind of a priori in common usage but hardly recognized as such, but it is the other kind of much more importance, that being, absent any element of experience whatsoever, that is, pure, which if not from experience, must the be from reason itself. Your list of a priori conditions on pg 1 are both kinds, but without the distinction of which is which. Conventionally speaking, that is sufficient, insofar as conventionally no one cares, but both scientifically and metaphysically speaking, it is very far from it. And, of course, you did ask a metaphysical question after all, so......just thought I’d weigh in. Or.....wade in, more like it. — Mww

As I noted, I found the discussions about pure vs. impure and analytic vs. synthetic, interesting and useful. I wasn't questioning their value, I was just expressing confusion. In my experience on the forum, many people use the term "a priori" to mean something that can be known without justification. Often, they aren't talking about tautologies or logical deductions, they are talking about metaphysical properties. My most recent example is causality - that all events are caused. I think there are good arguments for this positions, but there are also good arguments against it. To claim it is a priori knowledge is to shut down debate.

Do you think there has been a satisfactory answer to that? — Mww

This discussion has been really interesting and satisfying for me. I've gotten a lot to think about.

The question, "why am I me?" is a meaningless question (many philosophical questions are) if you understand that you are the result of a causal chain of events, and that if there was a different chain of events, it would not be that you would be some one else, rather you wouldn't exist at all. — Harry Hindu

But the question is why you are that particular combination of particles originating near the big bang leading to the life you lead from baby on. Why are you not another combination of particles leading to, for example, a current crocodile?

So Kant's pure reason is a priori reason? — Haglund

Kant describes what he means by “pure”, that being absent all elements of experience. Even if describing a priori with it, I think it safe to apply the term to reason as well. I don’t recall Kant defining pure reason as such, but usually just meaning how reason itself is to be understood from its use.

To be somewhat technical, understanding is the faculty of rules, reason is the faculty that unites the rules under principles. All principles are a priori and all rational deductions are free from empirical conditions, so.....

many people use the term "a priori" to mean something that can be known without justification. — T Clark

Again, technically, nothing can be known without some kind of justification, the possible exception being knowledge acquired by sheer accident, which merely indicates neither experience nor logic suffices.

The Greeks liked to divide knowledge into knowledge of and knowledge that. Russell called it knowledge by description and knowledge by acquaintance. Either way, the dichotomy reduces to knowledge before submission to the cognitive system and knowledge as a result of the system. Like..... I know I just got bit, but I don’t know what bit me. That I got bit is not something the least a priori knowledge, for it is an affect of some kind on the senses, and if I don’t know what bit me, that can’t be a priori because it isn’t anything.

Regardless, if one thinks knowledge to be a relative condition of certainty, that is only possible by being justified by something.

Or so it seems.....

Regardless, if one thinks knowledge to be a relative condition of certainty, that is only possible by being justified by something. — Mww

I agree with this. Some people seem to think that just saying "a priori" is all the justification that's needed.

Just wanted to say thanks for the dialog. You’re one of the single digit of posters whose feedback I’d not lightly dismiss, even if I’m in total disagreement with a few of them.

Your profile says you're Indonesian, not an "American white guy".

If there is more than one universe then are we not already acknowledging that there are a number of universes, and that there might be different universes where there are two universes in which 2+4=4 and 2 in which 2+2=7, but there are 2+2=4 total universes? — Harry Hindu

That would be a meaningless question if the sum of two and two is not objectively meaningful. You’re asking an objective question there, not one related to a particular set of laws.
You said that 2+2=4 is true in our universe, which I’ll call U0. So U0 → 2+2=4
But I’m going for a relation in the other direction: 2+2=4 → U0, U1, etc.
If mathematical law holds objectively and not just relative to our universe, then I can explain the existence relative to us of our universe. That’s why I’m interested in it being objectively true. It has been a weak point in my argument.

Would it make any sense at all to say that we can add 2 universes to 2 other universes to get 4 universes yet 2+2 does not equal 4 in a certain universe?

I suppose in the universe where 2+2=7, there would objectively be 7 universes, but we’d count only 4. That sounds like a contradiction since it is an objective quantity being discussed, not a quantity of anything that is part of one universe or another. That’s fair evidence that 2+2 objectively is 4, but I’ve not enough of a formal mathematical background to assess the validity of that argument.

You misunderstood what I wrote then. I was trying to illustrate why the ‘why am I me’ question is baffling only if dualism is assumed.
— noAxioms
Because you are assuming that there is an I that is separate from the individual (dualism).

The question assumes that, yes. Hence I rationally reject the question as either meaningless or begging. The question “why is there something and not nothing” is similarly meaningless/begging, and is why I abandoned the realism that it begs.

Dualism is indoctrinated at an early age with the introduction of religion (soul vs body).

I might agree with the solipsism thing, but my suspicion is that language is what then introduces the dualism, just like it introduces object identity and reinforces presentism, something that babies/animals already have. Religion (organized religion at least) is just a parasitical entity evolved to prey on these beliefs and the natural resistance to death.

Rationally, I’ve rejected all those things, even fear of death. But just rationally. I obviously hold multiple self-contradictory beliefs. As I said, the lies make you fit, and I’d not survive the day without them.

The notion that you can exist independently of your body is a delusion created as way to deal with the knowledge of your death.

Yes, warm fuzzies so you can sleep. Most people rationalize the lies rather than rationally analyze them, but most people don’t give a philosophy forum a second thought.
I’ve watched my mother rewrite her memories as a method of holding on to the warm fuzzies. It’s harder to see yourself do it, but it’s a necessary coping mechanism. Humans are excellent at rationalizing, but incredibly poor at rational thought. I struggle to be otherwise, and maybe even fool myself into thinking I’m on some kind of right track, but deeper down I realize that’s probably a rationalized conclusion. Go figure.

There is no lottery. There is no luck.

Agree, but you expressed incredulity about the bug, so I thought I’d explain from where that idea came.

Just wanted to say thanks for the dialog. You’re one of the single digit of posters whose feedback I’d not lightly dismiss, even if I’m in total disagreement with a few of them. — noAxioms

Thank you. I appreciate that. I can say that same about you. :up:

Your profile says you're Indonesian, not an "American white guy". — noAxioms

My profile actually says that my location is Indonesian fields, not necessarily that I am Indonesian, but then don't believe everything that you read on a person's profile. :wink:

That would be a meaningless question if the sum of two and two is not objectively meaningful. You’re asking an objective question there, not one related to a particular set of laws.
You said that 2+2=4 is true in our universe, which I’ll call U0. So U0 → 2+2=4
But I’m going for a relation in the other direction: 2+2=4 → U0, U1, etc.
If mathematical law holds objectively and not just relative to our universe, then I can explain the existence relative to us of our universe. That’s why I’m interested in it being objectively true. It has been a weak point in my argument.

Would it make any sense at all to say that we can add 2 universes to 2 other universes to get 4 universes yet 2+2 does not equal 4 in a certain universe?
I suppose in the universe where 2+2=7, there would objectively be 7 universes, but we’d count only 4. That sounds like a contradiction since it is an objective quantity being discussed, not a quantity of anything that is part of one universe or another. That’s fair evidence that 2+2 objectively is 4, but I’ve not enough of a formal mathematical background to assess the validity of that argument. — noAxioms

For it to be objective, it would have to be true regardless of what is true in each universe. It would be true outside of all the universes. If there is only one universe, then there isn't a problem.

Like I said, it doesn't make any sense to say that we can count universes - which is an act that we can only do if we put ourselves outside of all universes - while in a particular universe counting works a different way. It's like saying that in one universe there is only one universe, when there are actually many. How would you acquire the truth if not by leaving this universe and going to another? The truth that there is only one universe isn't true within a particular universe. It can only be true if you are outside of all universes.

I admit that this is all challenging my ideas of objectivity vs. subjectivity and my ability to communicate how I am trying to conceive them. But I think that ultimately we need to go back to what I said before that counting itself seems dependent upon (mental) categories prior to what is being counted. You can only count cats if you have a "cat" category that individual members are a part of. If you have no "cat" category, then there is only one of each individual animal. The same can be said of universes. What qualifies a universe to be a universe, or part of the category, "universe"? It seems that needs to be answered before we can even begin to wonder if there is more than one in the first place. So the question is, do (mental) categories exist independent of minds? Are categories objective features of reality?

I obviously hold multiple self-contradictory beliefs. As I said, the lies make you fit, and I’d not survive the day without them. — noAxioms

For me, it is the ironing out of the self-contradictory beliefs that make me fit. All knowledge must be integrated. It's more likely that your self-contradictory beliefs have no bearing on your goal to survive, which is why you can hold them and still survive. When you actually apply those beliefs to goals that they have an impact on, then you will find that your goals cannot be realized.

Yes, warm fuzzies so you can sleep. Most people rationalize the lies rather than rationally analyze them, but most people don’t give a philosophy forum a second thought.
I’ve watched my mother rewrite her memories as a method of holding on to the warm fuzzies. It’s harder to see yourself do it, but it’s a necessary coping mechanism. Humans are excellent at rationalizing, but incredibly poor at rational thought. I struggle to be otherwise, and maybe even fool myself into thinking I’m on some kind of right track, but deeper down I realize that’s probably a rationalized conclusion. Go figure. — noAxioms

That's the thing that we need to iron out. Is our goal to feel warm fuzzies and cope with the reality of life, or is to acquire true knowledge of reality? When we are discussing what is the case independent of ourselves, then bringing your emotional state into the discussion isn't useful at all.

&

The Greeks liked to divide knowledge into knowledge of and knowledge that. Russell called it knowledge by description and knowledge by acquaintance. Either way, the dichotomy reduces to knowledge before submission to the cognitive system and knowledge as a result of the system. Like..... I know I just got bit, but I don’t know what bit me. That I got bit is not something the least a priori knowledge, for it is an affect of some kind on the senses, and if I don’t know what bit me, that can’t be a priori because it isn’t anything.

Regardless, if one thinks knowledge to be a relative condition of certainty, that is only possible by being justified by something. — Mww

You seem to be describing the difference between belief and knowledge, not different kinds of knowledge. Beliefs seem to be those interpretations of sensory data from a single sense, while knowledge seems to include justification from all the senses. How do you know that you were bitten if you don't know what bit you? After all, it could be that you stepped in a claw-trap. You interpreted a single sensory perception (tactile) based on previous experiences of being bit, rather than confirming with your eyes what the source of the tactile sensation is. When you use your eyes, you are getting real-time information about the circumstances, not from the past in the form of memories or past experiences.

Now our eyes can "lie" to us too. Initial visual observations can lead us to believe that water is on the ground (mirage) when there isn't. It isn't until we make more observations, like moving towards the "pool of water" and observing it disappear that we go from justifying based on prior (and possibly outdated) experiences (information) to justifying based on current experiences (information). So by accumulating more observations over time, can we say that we have acquired justification for what it is that we claim that we know. So the difference seems to be the degree of justification. Ideas based on preliminary observations that have not been confirmed using real-time information of other senses qualify as beliefs. Ideas based on the information acquired by more than one sense, and over a period of time, and is confirmed with current observations, is what qualifies as knowledge.

Essentially, the difference between beliefs and knowledge is that beliefs are justified by either empiricism or rationalism alone, while knowledge is justified by using both together.

I am not sure if I have posted a comment before in this thread but the answer is simple. Watch a toddler...when we come to this world, we know nothing. Our culture expanding through time, provide us with all the axioms and principles etc realized by previous generations.
ALL our knowledge is empirical. All are axioms are tested empirically every time we use them. Even logic has rules that are grounded in the empirical ''face" of the reality we experience.
You won't be able to point to "a priori, self-evident, intuitive, obvious, and common sense." without first experiencing and interacting with other members empirically.

Btw on intuition, Nobelist Kahneman won his Award by exposing the untrustworthy nature of intuition.

You seem to be describing..... — Harry Hindu

Good that it only seems.

I am not sure if I have posted a comment before in this thread but the answer is simple. Watch a toddler...when we come to this world, we know nothing. Our culture expanding through time, provide us with all the axioms and principles etc realized by previous generations.
ALL our knowledge is empirical. All are axioms are tested empirically every time we use them. Even logic has rules that are grounded in the empirical ''face" of the reality we experience.
You won't be able to point to "a priori, self-evident, intuitive, obvious, and common sense." without first experiencing and interacting with other members empirically. — Nickolasgaspar

I'm generally in agreement with you, although I think you've made too strong a statement. It is my understanding that our brains and minds are built with capacities, structures, that provide a framework for processing our experiences. This shows up with language especially but also other cognitive functions. As I noted in an earlier post, studies have shown that very young babies have what appear to be built-in capabilities for numerical and moral judgements.

Yes Human brains have the capacity for numerical and moral judgments, grammar etc. After all we are the evolutionary product of billion of generations interacting empirically with their environment and its rules.

It's like saying that in one universe there is only one universe, when there are actually many. How would you acquire the truth if not by leaving this universe and going to another? — Harry Hindu

Acquisition of what amounts to a measurement of an unmeasurable thing is of little concern to me. Not being a realist, I don’t give meaning to realist statements like “there are X many universes”, be X 0, 1, some other number, finite or otherwise. My universe is confined to a limited distance. That’s a relation relative to any given event (physics definition) in my life.

Very late edit:
Is 2+2=4 a realist statement? Is it conditionally true only if either quantity is real or there are real things that can be quantified, or is it unconditionally true even without there being anything real to count? I can make it a little harder by picking a non-integer since it eliminates the relevance of just counting things.

What qualifies a universe to be a universe, or part of the category, "universe"?

Tegmark listed four different ways to do that. His first is the kind I referenced above, a set of finite sized hyperspheres that overlap, separated only by distance. That’s four different ways to define a cat.
I’m the first to admit that defining a word is a human language thing. It isn’t a physics thing at all. What delimits the cat from the not-cat? At exactly what point does the cat and food system become just cat?
In Dr Who, a character had a teleport device strapped to his wrist. Hit the button and you’re suddenly somewhere else. My immediate (no hesitation) reaction to that was to ask how it knew what was you and what wasn’t. In terminator it was a nice define sphere and if your foot was outside that line, it doesn’t go with you. But the wrist device needed to know apparently that the clothes needed to go with you, but not say the post against which you’re leaning, despite the post being closer to the device than many of your body parts. It really bothered me, never mind the whole impossibility of the device in the first place, which I readily accept as a plot device.

So the question is, do (mental) categories exist independent of minds? Are categories objective features of reality?

I’d have said that abstract is abstract and there is no cat until something names/models it. The word cat is strictly a mental construction. So are atoms if you come right down to it, but at least atom has a physics definition that the cat lacks. I’m not asserting anything here, just giving my thoughts.

It's more likely that your self-contradictory beliefs have no bearing on your goal to survive, which is why you can hold them and still survive.

The lies have a huge bearing on my ability to survive. So it must be the rational beliefs, far more likely to be true, that have no bearing. I’d say they do, but the rational side isn’t in charge, but instead has a decent advisory role for matters where the boss hasn’t a strong opinion. Fermi paradox solution: Any sufficiently advanced race eventually puts its rational side sufficiently in charge to cease being fit.

When you actually apply those beliefs to goals that they have an impact on, then you will find that your goals cannot be realized.

I have to admit that the rational side is like an engineer, not having goals of its own, but rather is something called upon to better meet the goals of its employer, even in cases where the goals are based on known lies. But I’m not sure whose goals you think are not being realized. They’re working on ‘live forever’.

That's the thing that we need to iron out. Is our goal to feel warm fuzzies and cope with the reality of life, or is to acquire true knowledge of reality?

OK, there’s a rational goal, since I rationally want to do the latter. Surprisingly, there are warm fuzzies on that road as well, despite the denial of that possibility from the theists, who assert oblivion as the only alternative to eternal orgasm in the sky.

Yes Human brains have the capacity for numerical and moral judgments, grammar etc. After all we are the evolutionary product of billion of generations interacting empirically with their environment and its rules. — Nickolasgaspar

We've been modern humans for only a short time. Our current morals are only a few generations old. Yes, there are some crude rules built into our instinct, but siblings regularly do some pretty cruel things to each other, so it's a stretch to say the morals are an evolutionary product instead of a product of society, and a rapidly changing one at that.

ALL our knowledge is empirical. — Nickolasgaspar

That simply is a conjecture. Do you have proof?

Unfortunately yes.

Unfortunately yes. — Nickolasgaspar

What's your proof then?

The mechanisms by which human societies manage to accumulated knowledge through time and become part of a diachronic culture.

Interesting, and it's no doubt what happens in the progress of knowledge. But knowledge needs a reference frame, a perspective, or a filter, to construct the empirical world with. The knowledge of these is not part of empirical knowledge. Without this a priori knowledge you wouldn't even be able to start the gathering.