The essential problem of universals is that we experience a world of particulars, yet our language is full of properties, relations, and kinds. That's because we also experience similarities among the particulars, allowing us to generate taxonomies, distill patterns, create models, and so on. If there were no similarities, we could not universalize. — Marchesk

I don't understand the problem. You say that "we experience a world of particulars" but also that "we ... experience similarities". So if particulars aren't problematic then why are similarities? We experience them both.

What needs to be explained is the similarities between particulars. Universals play this role well, but they do so at the cost of being strange and hard to accommodate, particularly in their more extreme forms.

How are they hard to accommodate? We describe the structure and behaviour of two particular things using (more or less) the same sentence. What's strange about this?

If we wish to keep universals out of our ontology, then particulars must fill the role that universals play in our language. We should be able to replace all talk of universals with particulars, and leave nothing out. So particulars must be able to explain the similarities we notice amongst them.

Perhaps; if you wish to keep universals out of our ontology. But why do you wish to do this? What, exactly, is the problem with saying that we use the single word "triangle" to describe the shape of two different particular things?

Noting that we can categorize particulars because we're able to assign predicates to them is to entirely miss the point. We already knew that. That's where the problem begins.

What problem? You just seem to have asserted that similarities are problematic, but it's not clear to me why they're problematic.

Because to express it this way would be to tendentiously make it appear that the properties of neutrinos are entirely constructed by us. — John

Well, as a supporter of model-dependent realism, I don't find this at all problematic. The physicist's model of the neutrino is just that; a model – a model used to describe and predict physical phenomena.

particulars are particulars because they are unique. — Marchesk

I would dispute this. A trope theorist would argue that the attributes that are shared are actually just particulars that are part of a set.

How about our knowledge of the particulars in question? Isn't that the successful comparison?

Then there is no problem because we know each particular and its relationships to other particular. We have as much "explanation" (it's really just description of the particulars we are talking about) as there is. What are we to make of similarities? How about, you know, recognising there are particulars which, by their nature (e.g. red, a tree, a car, happy, sad, etc.,etc.) are similar? Is it so hard to think that there are some things which are similar to other things by their existence as a particular?

Any question go "moving to subatomic particles" is irrelevant. Rather than trying to give an account for a similar particular by some other state of existence, we have finally learned we are talking about given particular, specific states of the world, which are similar (or different) to each other. Two objects are red by each object, each particular, being red.

With respect to science, this is actually quite an important point. The notion of "universals" leads to the mistake of trying to define states of existence through ideas. We start talking about things "human nature," as if there are a particular set of qualities which all humans will necessarily possesses, even though the world may end-up doing something different (e.g. humans born without arms, without eyes, with superpowers, etc.,etc. ). We stop looking at the particulars we need to for description of the world, instead trusting we know a "universal" which must grant us knowledge of existing states, to a point where we think no longer have to think about or describe a state itself.

Yes, but a model which doesn't model anything is not much of a model.

I don't understand the problem. You say that "we experience a world of particulars" but also that "we ... experience similarities". So if particulars aren't problematic then why are similarities? We experience them both. — Michael

It is accounting for the similarities that is problematic. We experience similarities among particulars. How is that? What is going on?

How are they hard to accommodate? We describe the structure and behaviour of two particular things using (more or less) the same sentence. What's strange about this? — Michael

For one thing, that universals are not bound to any single location. And for another, that particulars somehow participate in, or share properties with the universals. And finally, that universals are not epistemic. We experience particulars, not the universals themselves. Although maybe an Aristotelian can clarify their position here.

Perhaps; if you wish to keep universals our of our ontology. But why do you wish to do this? What, exactly, is the problem with saying that we use the single word "triangle" to describe the shape of two different particular things? — Michael

You're the one who has been challenging realism about universals in this thread, which would mean to keep them out of one's ontology. I was just explaining what that amounts to. If there are no universals, then particulars must do the work instead. That's all.

I would dispute this. A trope theorist would argue that the attributes that are shared are actually just particulars that are part of a set. — darthbarracuda

Maybe so? If tropes can do the work, then there is no need for universals in one's philosophy. The question is can they? I take it that's an ongoing debate.

One issue for tropes is that they are themselves strange. The notion of abstract particulars is bound to draw similar stares of disbelief as universals do.

To put the problem as simply as possible, particulars are particulars because they are unique. And yet these unique particulars seem to have attributes which are not unique. It is those non-unique attributes which permits us to generalize. What needs explaining is how unique particulars appear to have non-unique features. — Marchesk

That's incoherent.

Since particulars are unique, any expression of aspect of them is unique, no matter any similarity. Two clones are most definitely not each other, no matter how much alike they look, think, sound, act, etc.,etc.

There are no non-unique features. Any feature of a state of existence, by definition, is of that state only, including in instances where a feature is similar to what is found in some other particular.

There are no non-unique features. Any feature of a state of existence, by definition, is of that state only, including in instances where a feature is similar to what is found in some other particular. — TheWillowOfDarkness

If that's the case, then how does our universalizing work at all? How is it that we can categorize anything, or notice relationships between any particulars? In a universe of 100% unique particulars, generalization is impossible.

Unless you want to argue that the mind imposes a structure on the world which doesn't exist. That we're the ones adding the similarities in. I suppose that's what conceptualism amounts to.

I didn't say it doesn't model anything.

Well why should we not say the predicates in the model are or are not reflective of the properties of what is being modeled?

I agree, I find Trope Theory to be lacking in explaining the similarity between tropes without the use of universals.

There is no such thing as universalizing. When we "generalise" or "universal," we are at best talking about a similarity found in many unique states and at worst mistaking our idea about a feature for describing a state of the world.

There is no "how" in sense you are expecting. Categorisation isn't a function of an existing object. It is only how we talk about it. Placing an object in a category is defined by how we exist using language. So is whether or not we recognise the relationships between states of existence. In either case, it is always a question whether we exist with the relevant experience. How do we categories? We have the experience, use language, which is the relevant categorisation. How do we tell the relationship between objects? We know how the objects in question relate to each other. It is all defined what we are doing, not by the nature of any object we might know.

We experience similarities among particulars. How is that? What is going on? — Marchesk

The same areas of our brain that "light up" in response to stimulus X also "light up" in response to stimulus Y. And they do so because stimulus X and stimulus Y behave in the same way. I really don't understand what's troublesome. If it's possible for one thing to behave in such-and-such a way then it's possible for another thing to behave in that same way.

You seem to be working on the premise that it's less problematic for each individual particular to behave in its own unique manner. But what warrants this premise?

For one thing, that universals are not bound to any single location.

I don't know what you mean by this. Just that two particulars in different locations each behave in the same way? Yes. But, again, what's strange about this?

And finally, that universals are not epistemic.

Well, that's not true. We do know about universals.

We experience particulars, not the universals themselves.

But earlier you said that we experience similarities and that universals are similarities. Therefore we experience universals.

You're the one who has been challenging realism about universals in this thread, which would mean to keep them out of one's ontology.

Well, no, because I reject realist ontology.

But if you need to keep universals out of one's (realist) ontology, and if universals are apparent, then clearly one's (realist) ontology fails.

But earlier you said that we experience similarities and that universals are similarities. Therefore we experience universals. — Michael

I stated that universals are an explanation for similarities, and that if one wishes to dispense with universals, then particulars must play the role of explaining similarities.

Well, that's not true. We do know about universals. — Michael

We know that we utilize universals in language. Whether they exist in the world somehow in addition to the particulars is the age-old debate.

I don't know what you mean by this. Just that two particulars in different locations each behave in the same way? Yes. But, again, what's strange about this? — Michael

No, it's rather that there is something else called a universal by which the two particulars share properties or relations.

Well, no, because I reject realist ontology. If, however, you want a realist ontology, and if universals are inconsistent with a realist ontology, and if universals are apparent, then clearly realist ontology fails. — Michael

Realism in this debate means there are universals in addition to particulars, either in the particulars themselves, or some other realm. Maybe there are other options, but the point is they exist somewhere outside of our thoughts and language.

You seem to be working on the premise that it's less problematic for each individual particular to behave in its own unique manner. But what warrants this premise? — Michael

I may have made a mistake here in my characterization of the problem. It's not just that particulars have similarities. It's that we universalize over all potential particulars to say things like gravity is inversely proportional to distance squared for all objects having mass. But of course we don't experience all matter, so how are we able to do that?

Or we can say that all apples have the properties X, Y, Z without ever experiencing all apples. That's different from taking 100 apples and lumping them in a category of similar traits. And yet we have a great deal of confidence that certain properties make an apple an apple, which differentiate it from non-apples.

This way of thinking seems wrong-headed. Better to say that particulars are also universals, and universals are also particulars. or perhaps rather that universality and particularity are properties of things.

Even though Kantians make a strong argument, the big problem with it is that our best scientific theories say something very different. They describe a deep time before us, leading up to us. Our very existence is explained by cosmology, astronomy, geology and evolution.

Kant's 'Theory of Nebular Formation', adapted by LaPlace, is part of the corpus of modern astronomy. So don't think that there's a contradiction between Kant's philosophical work and science; there isn't.

No, it's rather that there is something else called a universal by which the two particulars share properties or relations. — Marchesk

And I think this is a category mistake. It's not that there is this particular, that particular, and a universal, just as it's not that there is a library, a classroom, and a university. You can't have a university without its "parts" and you can't have a universal without its particulars (i.e. you can't have something that things have in common if you don't have things to have something in common). But just as we don't then conclude that universities aren't real we shouldn't then conclude that universals aren't real.

This is why I pointed out that the very question "are universals real?" is mistaken. What you should ask is "is X a real universal?" And if X is something that many particulars have in common then X is a real universal. It is an empirical fact that many particulars have things in common (shape, size, colour, etc.) and so it is an empirical fact that these things (shape, size, colour, etc.) are real universals.

It's that we universalize over all potential particulars to say things like gravity is inversely proportional to distance squared for all objects having mass. But of course we don't experience all matter, so how are we able to do that?

I don't understand. We do it by doing it. We say "gravity is inversely proportional to distance squared for all objects having mass" and then if this statement successfully describes (and predicts) every experiment then we say that it is true.

Are you just asking "why is a single sentence able to describe many different instances of empirical phenomena?" Well, we don't know why. And conversely, if reality were different then we wouldn't know why a single sentence isn't able to describe many different instances of empirical phenomena. Some things are inexplicable.

And yet we have a great deal of confidence that certain properties make an apple an apple, which differentiate it from non-apples.

This sounds like essentialism, and as I argued here, essentialism doesn't really work.

Maybe there are other options, but the point is they exist somewhere outside of our thoughts and language.

Well, if the property of this particular "exists outside thoughts and language" and if the property of that particular "exists outside thoughts and language", and if both of these properties are described using the same term (e.g. "negative charge"), then a property which different particulars have in common "exists outside thoughts and language".

The contradiction comes from stating that we can't get outside our perspective to say what the world is like without us, and yet very important and successful scientific theories do exactly that.

But just as we don't then conclude that universities aren't real we shouldn't then conclude that universals aren't real. — Michael

Well, Some philosophers don't think that universities are real.

What you should ask is "is X a real universal?" And if X is something that many particulars have in common then X is a real universal. It is an empirical fact that many particulars have things in common (shape, size, colour, etc.) and so it is an empirical fact that these things (shape, size, colour, etc.) are real universals. — Michael

Does this imply a kind of strong emergence for universals then? Could you have predicted the existence of universities from their parts before there were any universities?

This sounds like essentialism, and as I argued here, essentialism doesn't really work. — Michael

Universals and essentialism seem related. If you accept that universals are real, can you still deny essentialism? You are agreeing that it's true that things in common share the same properties.

I don't understand. We do it by doing it. We say "gravity is inversely proportional to distance squared for all objects having mass" and then if this statement successfully describes (and predicts) every experiment then we say that it is true. — Michael

Yes, but it's saying more than that. It's saying that it's true for the entire cosmos, which is impossible to test. We have an expectation that when we come across new stars or galaxies, the same principle will apply. That's what makes it universal.

Yes, but it's saying more than that. It's saying that it's true for the entire cosmos, which is impossible to test. We have an expectation that when we come across new stars or galaxies, the same principle will apply. That's what makes it universal.

I think you're using "universal" in a different manner here. But regardless, what's problematic about this? We say that it's true for the entire cosmos, and if it successfully describes and predicts all relevant phenomena then it is and if it doesn't then it isn't.

We say that it's true for the entire cosmos, and if it successfully describes and predicts all relevant phenomena then it is and if it doesn't then it isn't. — Michael

It's not a problem if one accepts the reality of universals. It is if one doesn't. Then you need to account for laws of nature some other way. To say that it just fits observation is to ignore the problem, which is to account for the existence of such principles.

It's not a problem if one accepts the reality of universals. It is if one doesn't. Then you need to account for laws of nature some other way. — Marchesk

Then accept the reality of universals. Many particulars really do have things in common. It's empirically evident. X and Y are both (correctly) described as having a negative charge or being circle. It's still not clear to my what the problem is.

Then accept the reality of universals. Many particulars really do have things in common. It's empirically evident. X and Y are both (correctly) described as having a negative charge or being circle. It's still not clear to my what the problem is. — Michael

I tried to explain, but it's been considered a problem in philosophy since the Ancient Greeks.

I suppose that all particulars are related, and that only by means of universals that limits can be drawn between particulars. An apple is not a doughnut. The relationship between the universal and the particular are defined outside of any particular universal and any specific particular. The habitual appearances we note are ongoing/changing all the time, their manifestations are infinite. If we suddenly find a variety of apple that is bred to have a hole in the middle we would have to change our concept of what it means when we say 'apple'. We would have expand the limits of what it means to be an apple.

A blind man can have no universal concept of color, just a a deaf man can have no abstract idea of sound. They are unable to imagine exactly what is meant by these terms.

Yes, but it's saying more than that. It's saying that it's true for the entire cosmos, which is impossible to test. We have an expectation that when we come across new stars or galaxies, the same principle will apply. That's what makes it universal. — Marchesk

This is disgusting scientism and essentialism, Marchesk. We do not say that gravity must be true for the entire cosmos. What we know is the states we have observed and these fit with the present description of gravity. We have the expectation new stars and galaxies will work by the same principle, and given what we have seen, this is a fair guess.

But it is not description of the new state or galaxy. To describe the galaxy, we still have to perform the observation work. It might be different to the stars of galaxies we do before. We can't proclaim our theory of gravity must be true everywhere. It can't be because states of the world are distinct and defined in themselves. There's always the possibility a given state works differently than ones we have observed before. We cannot proclaim a theory must apply to the entire cosmos. Such a "universal" is impossible because each states of the world is its own thing.

What makes it disgusting? GR and QM are said to apply to the entire cosmos. It is an inference that can be shown incorrect, but the problem of universals is that we so readily universalize over particulars.