On the dangers of believing that types aren't real

Humans can't help dividing up the world into types. After all, it would be incredibly inconvenient to be only able to talk about particular things and not the types to which they belong: why spend hours saying 'I like Fido, and Rex, and Spot ...' when I can say 'I like dogs' in a second or two? Regrouping particular things in conceptual 'boxes' allows us to make generalizations about such things, like 'dogs bark', which in turn enables us to predict future events ('the new neighbors have a dog, so we should expect to hear barking') and to draw probabilistic and explanatory inferences ('Spot keeps barking, he must be a dog', 'Rex barks because he is a dog').

This 'carving up' of the world has always been of great interest to philosophers. As we have seen, many philosophers take our categorizations to be somehow reflective of the world's real structure. The world, on this picture, is already divided up into real groups of things that resemble each other, and our categories simply correspond to such groups. Philosophers in this camp then propose explanations, like realism and trope nominalism, as to why the world is like that.

There are those, however, who dismiss the picture of a pre-divided reality. For them, types are useful ways of classifying particular things, and nothing else. The world has no preexisting 'architecture' that our concepts may or may not delineate. In fact, a completely different way of classifying things would be no more 'real' or 'accurate' than our way. A classificatory system that included the type 'shdog', where something is shdog if it is either a dog or a tree may be far less convenient than one that includes 'dog' and 'tree', but it wouldn't be any less real. On this view, types are very much like the constellations navigators used to find their way around the sea: constellations like Ursa Major are useful ways of mentally grouping individual stars, but at the end of the day, only the stars are real (Nanay 2007). Likewise, for philosophers in this second camp, types usefully regroup the individual things that come under them – their respective tokens – but only the tokens are mind-independently real. Rex, Fido and Spot are real enough, but ‘dog’ isn’t.

Philosophical positions that embrace a picture of this second sort abound: conceptualism, predicate nominalism, conceptual relativism (Putnam 1999), irrealism (Goodman 1975), singularist semirealism (Nanay 2007). For our purposes, I will call the rejection of types as mind-independently real ‘type-antirealism’. In my experience, it is popular among college students, particularly in the arts and humanities, who often talk of types as ‘social constructs’.

Undeniably, some types are mere constructs – ‘shdog’ is one of them, and I’m sure you can think of others. However, I’m going to briefly argue that dismissing all types as mere constructs may come at a high cost.

Take the type ‘dog’. The type-antirealist tells us that ‘dog’ is just one way of classifying individual things. We may as well have used the type ‘shdog’ which, once again, regroups all and only dogs and trees. ‘Dog’ is more useful than ‘shdog’, but there is no reason to consider it as any more real.

Notice that the reality of ‘dog’ has been denied on the basis that there are other types which, while less useful, are surely (we are told) no less real. But if this is an acceptable way of denying something’s mind-independent reality, then why stop at types?

Take, for instance, a token of ‘dog’, say, Spot. Spot seems about as real as anything. But ‘Spot’, like the other objects of everyday life, is just one way of mentally grouping bits of matter together. Consider instead ‘Spot*’, the composite object consisting of the dog Spot and my mobile phone. Sure, ‘Spot*’ is a much more inconvenient way of regrouping bits of matter than ‘Spot’. But why think that Spot* is any less real than Spot?

The natural reaction here is to say that Spot clearly is more real than Spot*. But it isn’t clear how we can argue for this without having to admit that, equally, ‘dog’ is clearly more real than ‘shdog’, on pain of inconsistency. For instance, we may say that Spot is real because the existence of Spot has plenty of predictive and explanatory power: Spot’s existence explains why I hear barking when I walk by the neighbour’s house, and allows me to predict that my hamster will die very quickly if he escapes to the neighbour’s garden. In contrast, the existence of Spot* doesn’t explain or predict anything that the existence of Spot and of my mobile phone don’t already explain or predict. We infer from this, using some version of Ockham’s razor, that Spot is real and Spot* isn’t. But if we infer this, we must also (again, on pain of inconsistency) infer the reality of ‘dog’ over ‘shdog’. We have already seen that ‘dog’ allows us to explain and predict quite a lot, and ‘shdog’ wouldn’t do nearly as well on that front.

At this point, the type-antirealist may bite the bullet and claim that Spot isn’t real either. All that is real, he could say, is mind-independent matter, and both types and tokens are just convenient ways of carving up matter.

Unfortunately, things may get worse for the type-antirealist. Take ‘matter’, the spatially extended stuff out of which the concrete things around us are supposed to be made. We generally think of our experiences as sometimes being of such external, mind-independent, material stuff, and other times as being illusory, as in dreams and hallucinations. This is very useful, because it allows us to predict and explain our experiences: the fact that my experience of getting my hand chopped off was only a nightmare explains why I don’t have an experience of lacking a hand the next day, and the fact that my experience of writing this article is not illusory allows me to predict a future experience of seeing the article published on my blog.

But there are other ways of interpreting experience. I could think that none of my experiences are experiences of mind-independent matter. Or I could think that those I would normally regard as illusory are not, and vice versa.

But as we have seen, the type-antirealist must hold that the explanatory and predictive usefulness of positing a thing’s reality does not warrant the belief that such thing is actually real – otherwise, he would have to admit that types like ‘dog’ are real since such types are explanatorily and predictively useful. Hence it seems that the consistent type-antirealist must also regard mind-independent matter as nothing more than a useful tool for organizing, interpreting and predicting experience.

To sum up, the type-antirealist, by disallowing the inference from explanatory and predictive usefulness to reality, ends up having to deny the reality, not only of types like ‘dog’, but also of individual things like Spot, and, finally, of the external world itself. What was intended as a relatively mild, sophisticated scepticism lands us in a scepticism of the most radical sort.

Perhaps the type-antirealist can find reasons to be sceptical about types that aren’t also reasons to be sceptical about individual things, or mind-independent matter. But I have yet to see such reasons.

So, what is the danger of believing that types aren’t real? It is that, if one is consistent, one may end up believing very little indeed.

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.