Humanity *in general* and *your* humanity both exist - the uses of 'trope platonism'

In a previous entry, we looked at platonic realism and trope nominalism. Recall, platonic realism holds that particular things of the same kind, e.g. humans participate in or instantiate the universal or form ‘humanity’, where forms/universals are immaterial entities existing in an eternal ‘world of forms’. Trope nominalism, in contrast, holds that particular things of the same kind have tropes that resemble each other. A ‘trope’ is sometimes referred to as a ‘particularized property’. We can speak of ‘humanity’ in general, but we can also speak of your humanity, and mine. Your humanity and mine may resemble each other, but they are not the same thing. Trope nominalists say that each of us has a ‘human-trope’, and this explains why we are both humans.

I argued in this entry that platonic realism can explain something that trope nominalism cannot – namely, the fact that resemblance exists at all – and that this a reason to believe that particular things do indeed participate in platonic forms. But the fact that particular things participate in platonic forms does not rule out that they also have tropes. Indeed, Michael Loux writes that one could advance a “two-step” theory, which “makes tropes constituents of familiar particulars” but in which the tropes themselves are “instantiations of universals” (2006, p.211). This is a picture in which you and I have distinct human-tropes, but each of our human-tropes participate in the platonic form of humanity.

If there are good reasons to believe, as I have argued, that there are platonic forms, and good reasons to believe that there are tropes, given that the two are not jointly inconsistent, it seems we have good reason to take seriously a hybrid “two-step” theory of this sort.

So, what reasons are there to believe in tropes? One could conjure up clever arguments for their existence, but as far as I’m concerned, it is enough that I can just see tropes. When I look at you, I see your humanity. When I look at myself in the mirror, I see my humanity.

Examples of this kind, at the very least, suggest that the idea of particularized properties fit nicely with our everyday linguistic practises. But those hostile to tropes will charge that we shouldn’t let our language dictate our metaphysics. Point taken.

What then, do I see, if not your humanity and mine? Let us consider other candidates.

1. Perhaps I see the same thing in both cases, that is, humanity itself. But this is a non-starter for those who believe ‘humanity’ to be a platonic form, since platonic forms are necessarily invisible. But of course, critics of tropes tend to be platonists, and thus will show little interest in this candidate.

2. Perhaps it is strictly incorrect to say that I see your humanity (and mine), and that saying as much is an informal shorthand for saying that I see that you are human. When I ‘see that x’, I see something which makes me know or understand that x (this is sometimes referred to as ‘epistemic seeing’, cf. Dretske 1969). But then, the critic owes us an explanation as to what this ‘something’ which makes me understand that you are human, is, which leads me to the next candidate…

3. Perhaps what I see is your appearance – your walking on two legs, your lack of fur, etc – and this leads me to know that you are a human, i.e. that you participate in the form of humanity.

This third account of what really goes on when I ‘see your humanity’ doesn’t involve tropes, unless we say that your human-trope just is your particular morphological structure. To use a simpler example, a critic of tropes might say that we don’t strictly see the yellowness of an autumn leaf, just the pigments that make the leaf yellow (Levinson 2006). But the trope nominalist, I argue, can simply answer that the yellowness of the leaf just is the collection of such pigments.

This answer presupposes that tropes are concrete constituents of particular things. Here it is common to protest that the trope nominalist has made a category mistake (e.g. Lowe 2007). Tropes are supposed to be particularized properties, and properties are not constituents or parts of objects. Rather, they are ways an object is.

Whether it is category mistake to say that particularized properties are constituents of the objects that have them is largely a conceptual matter: if our concept of a particularized property, like ‘your humanity’ rules out its being a constituent of particular thing (in this case, you), then to say that your humanity is a constituent of you is to misunderstand the relevant linguistic conventions. But while it might violate the linguistic conventions followed by some metaphysicians, I don’t see how it violates the ‘folk’ linguistic conventions of wider society. As far as I can tell, we find it quite natural to think of the particularized properties of objects as constituents of such objects -- is it really ‘absurd’ to say that the autumn leaf’s yellowness is a part of the leaf?

Granted, metaphysicians are free to use concepts as they please. But it seems to me that, if we are to communicate something of value to those outside the field, it is the linguistic conventions of wider society that our theories ought to respect. Hence, if I am right to say that the everyday concept of a particularized property (your humanity, this leaf’s yellowness) allows it to be a part of an object, we shouldn’t regard the claim that tropes are constituents of things as a category mistake.

Hence why I persist in my belief that I do see tropes. If I do in fact see tropes, then a fortiori they exist. But, as we have seen, I also think that platonic forms play a unique explanatory role. So, at the risk of being too greedy, I’m going to have both: objects have tropes, and tropes participate in platonic forms. Call this 'trope platonism'.

Levinson, J. (2006). Why There Are No Tropes. Philosophy, 81(04), 563. doi: 10.1017/s0031819106318013

Loux, Michael (2006). 8. Aristotle's Constituent Ontology. Oxford Studies in Metaphysics 2:207.

Lowe, E. (2007). The four-category ontology. Oxford: Clarendon.

Does evolutionary theory contradict Platonic realism?

Evolutionary biologists don't tend to like Plato very much. Consider the following quote from Richard Dawkins:

" If, like Aristotle, you treat all flesh-and-blood rabbits as imperfect approximations to an ideal Platonic rabbit, it won’t occur to you that rabbits might have evolved from a non-rabbit ancestor, and might evolve into a non-rabbit descendant."

Dawkins explicitly draws on the renowned evolutionary biologist Ernst Mayr, who argued that the "dark hand of Plato" was the reason why evolutionary theory took so long to be (almost) fully accepted in the West. I will briefly address the above criticism and some others in this entry.

The thought here is that if one believes that members of a species all reflect the same unchangeable form, one is unlikely to accept that the ancestors of the members of this species belonged to a different species. Dawkins and Mayr may be right that Plato's influence has contributed to the great resistance to evolutionary theory, and even that platonic realism itself makes evolutionary ideas seem unintuitive. Nevertheless, it is important to emphasize that nothing in the theory of platonic realism contradicts the notion that a given species can evolve from another species. This is because the claim that all members of a species participate in the same form is perfectly compatible with the claim that said members have a disposition to bring about (however indirectly) members of a different species, who participate in a different form.

A more worrying objection is voiced by Prof Volker Sommer, a primatologist at UCL. Sommer argues that the categories that species constitute have "blurred edges". The evolutionary account of biological diversity entails that, rather than being discrete, sharply distinguished 'boxes', species are continuous with one another, in much the same way that colors are. Thus, just as there is no sharp boundary between orange and red, there may be no sharp boundaries separating two species, which means that there will be 'borderline' cases where there is no fact of the matter as to whether a given organism belongs to one species or another.

Sommer suggests that, because of this, there is a sense in which, far from merely defining preexisting "borders of the world", zoologists "create worlds". That is, the species to which an organism may or may not belong is a convenient artificial grouping, rather than a real or natural one. We create such artificial groupings all the time: for example, I might conceptually group some human beings under the name 'friends', and others under the name 'acquaintances'. Groupings like this are practically useful, because they help me navigate the complex world of human relationships (for example, to decide whose email to answer first, and so on). But they aren't real, in the way that we'd expect species to be real.

Interestingly, when I took his module back at UCL, I once heard Sommer say in a lecture that it was ironic for Darwin to have named his book The Origin of Species, since his theory implied that there really are no such things as species.

But if species aren't real /natural groupings, they can't be said to reflect forms -- as we saw previously, part of the point of positing a realm of forms is to explain why such real groupings exist.

This problem is well-known to philosophers of biology, and there is no way a single blog entry could do it justice. Hence I will content myself with a few points:

1. The objection, at most, shows that members of the same biological species don't participate in the same form. This is much more modest than saying that no grouping is made up of things participating in the same form. Realists don't need to believe that all the names and categories we use are real and not artificial, and hence linked to their respective forms. Few, for instance, would say that there is a form of the 'democrat' or of 'being an acquaintance'.

2. The objection relies on an inference from 'this grouping has vague boundaries' to 'this grouping is artificial, rather than natural'. But it really isn't obvious that a grouping doesn't have anything to do with the real structure of the world if it has borderline cases. Take two kinds, 'bird' and 'zird'. Something is a member of 'zird' if it is either a bird or a mobile phone. 'Zird' is an artificial grouping if there ever was one. The evolutionary story tells us that members of the kind 'bird' are descendants of the kind 'non-avian dinosaur'. This means that there almost certainly have existed organisms for which it is vague whether they belonged to 'bird' or 'non-avian dinosaur'. So 'bird' has vague boundaries. But it just seems wrong to say that 'bird' is on par with 'zird', both being equally artificial groupings. For one thing, that an animal exemplifies 'bird' explains much more than that it exemplifies 'zird'. The fact that Pete the parakeet is a member of 'bird' explains quite a lot about Pete, e.g. the fact that he has feathers and a beak. Indeed, these traits are what we would expect of a member of 'bird'. In contrast, the fact that he is also a member of 'zird' explains very little about him. It may perhaps explain the fact that he is a material thing, since all members of 'zird' are material things. But this explanation in terms of being a zird is totally unnecessary, as the fact that he is a bird can explain this just as well (since all birds are material things).

Of course, those suspicious of allegedly 'natural' groupings could retort that this just makes 'bird' more useful than 'zird', not any more real (see Nanay 2011 for a view along these lines), since it helps us make more predictions about the features of members of 'bird'. I would tentatively submit that high explanatory and predictive power is just part of what it means for a grouping to be 'natural'. In fact, I can't really see what more one could ask of a given grouping for it to genuinely count as 'natural', i.e. somehow reflective of the structure of nature. In that case, saying, 'I see that the grouping 'bird' helps you explain and predict many features of the members of 'bird', but is it a natural grouping?' would be conceptually confused, like saying 'I can see that you are single and male, but are you a bachelor?'.

If I'm right, the fact that species (like Homo sapiens) have vague boundaries does not imply that they are purely artificial groupings, and hence that they cannot have a corresponding platonic form, which their members participate in.

These responses to Sommer's objection may not be decisive (at least in their current form), but they should at least give evolutionary biologists an opportunity to reconsider their natural aversion to platonism.

No demiurge, no forms

The last entry discussed realism, the view that there exist universals (traditionally known as 'forms'). As we saw, on realism, objects that share properties, e.g. two red objects, are said to exemplify or participate in the same universal, in this case, the universal 'redness'. Realists generally regard universals as abstract, existing in a realm causally disconnected from the realm of concrete things that we exist in.

I argued that a benefit of realism is its potential to explain why the world contains what might be called 'real resemblance groupings'. Things in the world, as it were, 'come in boxes', i.e. in natural categories that our concepts try to demarcate. Trope nominalists explain this by saying that things belong to the same real resemblance groupings because the individual properties ('tropes') they have resemble each other (e.g. the redness of object 1 resembles the redness of object 2), and leave it at that, leaving resemblance as an unexplained brute fact. The realist explanation goes further, as it explains why resemblance exists at all. Resemblance between concrete things in the world is ultimately explained by their participation in abstract universals.

However, I noted that realism faced various troubles. I will mention two:

1. Unintelligibility: the reader may have noticed that, frustratingly, I have used phrases like 'participate in' and 'exemplify' without ever explaining their meaning. Unfortunately, such sloppiness on my part reflects the very real problem that we are rarely, if ever, told by realists what it means for a thing to 'exemplify' or 'participate in' a universal. This is a serious weakness. Recall, the exemplification of / participation in universals is supposed to explain the existence of real resemblance groupings. But a purported 'explanation' can't do any explanatory work if it is unintelligible. Suppose my 'explanation' for the existence of real resemblance groupings is that they are 'troxed by gromphles'. It wouldn't do for me to criticize trope nominalists for offering an incomplete explanation of real resemblance groupings, as the 'explanation' I put forward is no explanation at all, since its meaning (if it has one) is impossible to understand. Of course, realists may answer that terms like 'exemplify' and 'participate in' are primitive, meaningful but impossible to analyze (like, perhaps, 'exists'). But in doing so they will be hard-pressed to convince their audience of the reality of what they are talking about. If I don't understand what the terms of the alleged explanation mean, I will never be able to accept the explanation itself.

2. Causal isolation: realists typically hold that universals are abstract, by which they mean that they are outside of space and time, and therefore causally isolated from the world of concrete things. That is, they cannot causally interact with such things. Two subproblems arise from this:

2a. if universals can't causally interact with concrete things, how can they be responsible for the real resemblance groupings in which concrete things find themselves?

2b. since you and I are concrete things, universals aren't causally related to us either. But this would seemingly make it impossible for us to know about them. Philosophers tend to accept the so-called 'causal theory of knowledge', which says that, for a knower to know a fact, there must be some sort of causal relationship between the knower and that which he knows. For example, I know that there is a cup on my desk because the cup's being on my desk causes me to have a perceptual experience of the cup.

It should be clear that the problems raised here are more than just unfortunate consequences of realism, that we just have to accept because we need realism to explain real resemblance groupings. Indeed, if these problems aren't dealt with, it turns out that realism can't explain anything at all.

I will now argue that these problems don't arise if the realist also believes in a demiurge. The demiurge (demiorgos = 'craftsman'), for Plato, was a God of some sort, who creates the concrete things of this world out of preexisting raw materials by modelling them on the perfect forms. Thus, things that belong to same real resemblance grouping do so because they were ultimately modeled according to the same form. Later platonists often interpreted the forms as eternal ideas in the demiurge's mind.

How does this more ancient variety of realism fare with respect to the foregoing problems?

1. Unintelligibility: to 'participate in' a universal is to be understood as having been modeled on this universal. This is much more intelligible than in the demiurge-less version of realism, because we know what it means for something to be modeled on something else. Moreover, if we take the later platonist view that sees universals as divine ideas, realism becomes even more intelligible, since we know what ideas are and we know what it means to model things on them (this current blog article has itself been modeled on my idea of a blog article on the importance of the demiurge to realism).

NB: this does not commit the realist to believing that the demiurge directly creates the members of real resemblance groupings, through spontaneous acts of creation. The demiurge could instead indirectly create them, by setting up the initial conditions and laws that would bring about the desired groupings. Hence, the theistic realism described here is compatible with scientific views of the development of the universe (more on this in another entry).

2. Causal isolation: in Plato's realism, the demiurge acts as a kind of causal bridge between the forms and the realm of concrete things. The demiurge contemplates the forms and crafts concrete things that reflect them. So, the universals are causally responsible insofar as they inspire the demiurge to create as he does.

Moreover, since real resemblance groupings are ultimately causally linked to the universals via the demiurge, the epistemic problem disappears as well. We can know about them by inferring their existence from the real resemblance groupings for which they are ultimately causally responsible.

If I am correct that this theistic realism has what it takes to deal with the problems of unintelligibility and causal isolation, the implications are significant. For one thing, it would mean that realists should think twice before minimizing the importance of the demiurge to Plato's original theory, to which they owe their realism. This may mean being compelled to choose between realism and atheism, which would be bad news for realists openly hostile to theism, like Russell. For another, this provides natural theologians with the basic constituents of an argument for theism: if we need universals, but can't have them without theism, then it looks like we need theism too.