Changeable Natural Kinds

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I've got a question for any philosophers who read this blog. I've encountered an issue that I know very little about and was interested if anyone knew the answer. Are there any views out there according to which there are natural kinds but something that is a member of a natural kind might cease to be a member of that natural kind and then be a member of a different one? I'm pretty sure Aristotle would never allow something like this, but I was wondering if any philosophers have defended such a view.


I assume you mean that the individual might change kinds without itself changing (e.g., in the way that individuals can change the groups they are in)? (For the individual to change kinds by changing itself would be just ordinary transformation of one thing into a different thing, e.g., a human body being decomposed into soil.) I haven't come across anyone who holds such view; it looks like it would defeat the purpose of talking about natural kinds in the first place. (Although, admittedly, there's a lot I haven't read in the literature on natural kinds.)

Not sure exactly the question you are asking?

As Brandon suggested, is it about individuals changing kinds? This kind of depends on how you (what properties) define those kinds. A tadpole could be considered a kind, and a frog another for some definitions of kind.

Alternatively, or you thinking more about Hillary Putnam's twin earth water example in 'The meaning of meaning'?

A frog and a tadpole are usually considered two stages of the same natural kind. There's no more genetic change there than there is from an embryo to an infant. It's the same organism. What I'm wondering about is whether there's a view out there according to which I might no longer have the natural kind Human and gain the natural kind Giant Bug With a Human Mind.

Would transsubstantiation qualify?

I'm not sure what the exact view is with transsubstantiation. Does it stop being bread and wine when it becomes flesh and blood? Does it remain the same substance after the change? If yes to both, then I think it qualifies.

With Transsubstantiation, the bread and wine transform into the body and blood of Christ, but they retain the outward accidents of bread and wine. So I guess it does stop being bread and wine when it becomes flesh and blood. If by "same substance" you mean the same matter, then yes it remains the same substance after the change. If by "same substance" you mean it has the same Aristotelian form, then no, it does not have the same form as it now has the form of body and blood even though it has the matter of bread and wine.

Does that make any sense?

Actually, although there's some leeway on what Catholics can believe about it, the one thing they all agree on is that the substance does not endure the change. It's the accidental forms that remain the same. (There's potential for conclusion here, because the species, or bread and wine, are considered to be the matter for the sacrament, and the words the form, but this doesn't have to do with the nature of the species themselves.) The idea is that the qualities of the bread cease to have matter (only in the Aristotelian sense -- matter in the modern sense means anything having mass, and mass would be considered an accidental form in the Aristotelian view), and cease to be accidents of any substance, having become grounded and sustained entirely by God's omnipotence.

Since natural kinds are what things are, it doesn't seem an individual could outlast a change of natural kinds. However, if one holds that an individual could have more than one natural kind, an individual of one kind could become an individual of another kind (although still remaining the same individual), by retaining the original kind as well. In a sense this would be one way to put the Chalcedonian view of Incarnation. But it seems that you need the first natural kind to endure the change in order to keep the individual the same individual.

I already know that on the Aristotelian conception of natural kinds you won't be able to have a substance that ceases to be of one natural kind and then comes to be of a different natural kind. For him the natural kind is what you are. What I'm trying to figure out is if anyone has defended the view that there are natural kinds but allowed for something of one natural kind to stop being of that natural kind and come to be of another natural kind.

Some examples might help. If my whole body gets gradually replaced by silicon-based stuff instead of carbon-based stuff, some people might think I survive the process. They might also think that I'm not longer human by the end of it but a new natural kind, all the while thinking that being human is a natural kind that I belonged to and no longer do. Some would say it wouldn't be me at the end of the process. Others might say that being human isn't a natural kind. But some might want to accept both things and then defend their consistency.

People who think we can survive by transferring our consciousness into a computer clearly think being human is not essential to our existence. If they additionally believe that being human is a natural kind, then they hold a view like what I have in mind. Many would say you don't survive or that being human isn't a natural kind, but someone might try to say both.

In neither case have I explained how being human can be a natural kind while allowing for the possibility of ceasing to be human and remaining the same individual. I've simply listed what sorts of views you'd have to put together for this sort of view. I'm wondering if someone has done the work of defending this combination of views.

It occurs to me that Lynne Rudder Baker might mention something characterizable in this way. I don't recall if she argues it as her own view, or just puts it forward as a view that might be held, but in *Persons and Bodies* she does talk about Kafka's story about a man turning into a bug while continuing to be a person, and draws some conclusion or other about its plausibility.

Well, if you are including identity into the mix (and it seems that you are), then transsubstantiation looks like a good fit to me.

The Host starts off as one natural kind (bread/wine) and ends up as another (body/blood), yet it always remains the Host. That the matter/accidents of the Host remains the same throughout helps to show that the new kind (body/blood) is still the same object as it was before the transformation.


The idea behind transubstantiation is that the bread and wine only become the Host, properly speaking, when they are the Body and the Blood. Use of the term 'Host' of ordinary bread and wine could only be a figure of speech, since being the 'Host' means having the real presence -- which on a doctrine of transubstantiation means that it has ceased having its original substance and is sustained only by the power of God. And as I said before, the matter, understood as substance (rather than as certain characteristics like mass and shape), doesn't remain, only the shape and other qualities do. It's precisely the point of transubstantiation that the species after consecration aren't the same object; they appear the same, but they are in reality as far apart in natural kind as bread and Christ, as matter and divine omnipotence.

The more I think of it, the more I think Baker's probably a case of what you're looking for, Jeremy; but I don't have Persons and Bodies with me, so I can't be sure.

Sorry... was sick yesterday.

As I was trying to say, it all depends on how you define 'natural kind'.

You seem to use genetics as the delimiter of a kind in this example. As such, this gives us a couple of things to think about.

1) Before, I referred to Putnam's 'Meaning of Meaning'. His example of water here being H20 and water on 'twin-earth' being 'xyz' although they have all the same properties otherwise shows that our definition of what is the same kind is open to reclassification when more knowledge is gained. (So before they worked out the chemical composition of water, both earth's and twin-earths water were considered the same kind, and afterwards they are distinct kinds). So one problem is how do you accurately define a kind? We may have the kind 'human' but maybe further investigation will reveal a essential difference (in quarkal composition maybe?).

2) Using genetics, there is no defining 'human' genetic code. Every persons DNA differs, so specifying a kind is problematic.

3) As water is H20, (and further protons, electrons, neutrons etc etc), it is possible that water can be turned into a variety of different chemicals and so become a different kind. (because ultimately everything is made up of combination of the same 'kind' of bits). Therefore change in 'natural kind' is possible.

4) This seems to be your real question - Does anyone defend the view that identity can maintained when something changes from one natural kind to another.

But this brings us back to the definitional problem. As you alluded to when you said "People who think we can survive by transferring our consciousness into a computer clearly think being human is not essential to our existence." Is 'I' simply a member of the 'human kind'. Anyone who believes in an immaterial soul would say no.

All this rambling leads me to the point that your question is logically contradictory.
To rephrase it you are saying - Does anyone believe that an essential property of 'I' is not an essential property of 'I'.

1 is just an epistemological issue. I don't see how that's relevant to the metaphysical question I'm asking about.

2. Well, I know there are these people who want to hang on to the notion of natural kind even though it seems as though there aren't any Aristotelian natural kinds on the standard evolutionary picture. If the difference between two species is just a matter of degree, and all the positions in between could have been occupied, then it seems hard to say what a natural kind is unless it's just whatever groups contingently formed without any actually existing intermediate forms. So right now frogs are a natural kind, and so are toads, but if all the spots on the continuum between them existed then they might not be separate natural kinds.

3. The physical components of a physical object can be rearranged into a new thing that is a different natural kind. That's not very controversial. I'm asking if the water would still exist but not as water.

Some people would say it's the same stuff, but would those be people who believe in natural kinds? If I'm just a hunk of matter, that hunk of matter will still exist once I'd dead. People who believe that might say that I will continue to exist as a corpse and then as a hugely scattered object. Do people who think that believe in natural kinds?

I don't see your point about a contradiction. That only follows if you assume that being of a natural kind is an essential property. But that's the question I'm asking. Does anyone deny that? It's not part of the definition of being a natural kind. Natural kinds are just joints in nature, but couldn't someone be on one side of a joint in nature and then be on another side while remaining the same person? It seems like a perfectly coherent view.

On the contradiction, that is just my point. If you accept that being a natural kind is not essential, then it is unproblematic in thinking something can change kinds. It's a no brainer once you work out the definition. (Something like what daniel dennett used as an example in 'where am i?' where his consciousness is transplanted to a computer brain)

(Maybe a little off track, but I have had too may philosophy assignments of late so I am just thinking aloud)
On being just a hunk of matter...I think this is why you can't ignore epistomological questions in this. The notion of a 'natural kind' is just a classification that makes it useful for grouping things that are alike in some way. Once the classification becomes not useful, it is discarded (so when a corpse becomes so decayed that it is no longer useful to keep it in the same classifcation it is no longer called a corpse). If you find out more information that invalidates some classification, it is changed.

This is my view of natural kinds anyway. It seems plain to me because when you try and determine why something is said to be of the same kind as something else, the answer always seems to revolve around a couple of things
1) Our incomplete knowledge about those things
2) Our somewhat arbitrary criteria for which differences do not invalidate something being in the same kind.

For instance, take the natural kind of 'human' from a Christian perspective. In thinking about what being 'human' really means (A) it could be
A1) A dualistic being - Physical/spiritual
A2) A transcendent being - Free will
A3) A moral being - duties and conscience

What it doesn't mean (B) is
B1) Any particular gender
B2) A particular hair colour
B3) having 5 fingers on each hand
etc etc etc

So what does it really mean to think of two things as 'human'? (What does it mean to think of any two things as the same kind?) Only that they are similar in the group of properties (A) that we have deciced are important for that kind. Other properties (B) are irrelevant.

I would suggest that when anyone has ever talked about natural kinds, it is this sort of thing. A group of properties that are considered necessary and sufficient to be a part of that kind. The question then becomes how or why some properties are put into (A) and not (B). I think it is because the categorisations are useful. We need to group things that are alike in certain properties because we use those properties in our day to day life. It is a short cut, like stereotyping, to understanding things quickly.

Ah well, I will stop rambling now

On the contradiction, that is just my point. If you accept that being a natural kind is not essential, then it is unproblematic in thinking something can change kinds. It's a no brainer once you work out the definition.

Yes, but I'm not wondering if anyone has defined it this way in order to get the ad hoc result that they want. I'm wondering if anyone has given an account of why we could think of natural kinds this way without doing something so ad hoc.

I'm not sure I agree with all your cases, by the way. I think of "male human" and "female human" as good examples of natural kinds in exactly the way that race seems not to be according to most intelligent views nowadays (though I'm going to end up arguing that that's less clear than some make it out to be).

Although all of these blogs are quite old now on the off chance that they are still active...

There are various contradictions within the literature on natural kinds, but as a specific response to your question: Joseph LaPorte's recent work on natural kinds argues that we in fact stipulate them (as opposed to discovering them). You are certainly right about Aristotle, and current figures in the literature also maintain this view of natural kinds, that there can be no cross over. What it really seems to boil down to is essence, and whether the essence of one entity could become the essence of another over time. Biological examples are farily decent to access this intuition. Imagine a case where a bird (A) evolves over time into what we would right now term as a bat (B), and that a bat evolves over time to what we would, again right now, call a bird. If biological kinds are in fact natural kinds (which is by no means certain) then where do your intuitions in this case lie? In this counterfactual case I am imagining that the species cross completely - which while conceptually possible might be disputed by biologists as actually possible (I'm not a biologist so I couldn't say)- and actually becoming indistinguishable right down to their genetic structure (so if one were a micro-reductionist this might be their essence). According to cladistics, and providing cladistics is what constitutes essence, then although these two species A and B cross on all intrinsic empirically available levels they cannot ever be members of the same kind. I find this counter intuitive as it stands, but what it highlights is i) a question about whether natural kinds are intrinsic, and ii) whether we discover natural kinds or stipulate them. A good place to view this kind of disagreement is Brian Ellis vs. Joseph LaPorte, as they disagree fundamentally about what a natural kind is. Also if you check the AHRC funded 'metaphysics of science' home page there is a large bibliography, which is being constantly updated.

Please excuse any spelling, I am in a bit of a hurry. However, if you are still interested in a dialogue I am more than happy to enter into one.

I'm not very big on views that take natural kinds to be stipulated rather than discovered. That just seems to me to be a denial that there are natural kinds.

But it is those views that I'm interested in with respect to this question, because they might affirm that something is a natural kind and then admit that what makes it a natural kind is not essential to it.

I'm not 100% sure what your point is. Is it that cladistics would mean this is a bird because of its ancestray and not a bat at any stage in its existence, merely because it needs to have different ancestry to be a bat? I don't find that all that implausible. I can imagine saying that the prince who is turned into a frog in the old fairy tale isn't really a frog but is just a human being who has all these intrinsic properties normally appearing only in frogs and lacking many intrinsic properties normally appearing in humans.

I'll have to check out LaPorte and Ellis. Thanks for the tip.

The cladistics point is especially relevant, since one of the two contemporary natural kind views of race in the literature (Robin Andreasen's) is a cladistic view.

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