More on nominalism v realism

I foolishly allowed myself to sidetrack the discussion of my own recent post
on these two major philosophical alternatives (nominalism and realism) into a conversation with Lou Jost on the TOE itself. I blame the fact that I was preparing the piece on neutralism and adaptationism, which nudged me out of philosophy mode. Not that the discussion hasn’t been interesting, even useful, in itself, but it has perhaps prevented the theists here from grappling with the important issues of the nominalist-realist question. So I want to spend just a few more words on it before moving on to another significant philosophical issue in a different post.

I pointed out in the previous column that Darwin’s evolution, and modern thinking generally, has tended to assume a nominalist position (that universal categories don’t truly exist) without necessarily realising it. Continua, especially gradualist evolutionary continua, are assumed not just in biology but everywhere. That’s partly because evolution has become such a pervasive meta-narrative in everything from morality to universes. Everything once considered discrete and specific has become an arbitrarily-divided spectrum, whether that be correct grammar or gender.

At the same time this is inconsistent because, in evolution for instance, universal categories such as taxonomic levels are most often treated as if they are real, as in the concept of nested heirarchies. This ought not to surprise us given our previous examination of final causation, which we found to be denied under naturalism even whilst it is extensively employed in discussing function and so on. Scientific medicine, for example, would be a dead duck if it had no concept of “normal function” to which patients can be restored: without the “ought” of final causation, there could be no therapeutics.

Medical “normality” also implies the reality of universals (the philosophical realism we have been discussing) as well as of final causation. Normality implies there is a standard from which the sick person deviates. Since nobody is “normal” in every respect, the goal at which medicine aims is a non-material ideal, a universal human form.

Universals are even broader than this, though. Philosophers argue about whether mathematics is a merely human construct, or a reality “out there”. There can be no doubt that to the working scientist it is the latter – mathematics is the language of science, and the validation of its universal truth (which is why biology suffers from physics envy!).  But mathematics of any sort is nothing but the manipulation of non-physical universals. Nobody can put the number 2 (or any other number) in a bottle. But if the whole human race died, would the ratio of a circle’s circumference to its diameter cease to be π?

To deny universals, then, may be a nice intellectual conceit, but like denying consciousness or free-will it is impracticable (did you hear, by the way, about determinist Jerry Coyne’s recent complaint that Daniel Dennett had been “unnecessarily” rude? Priceless). Accepting realism in theory doesn’t necessarily guarantee that there are such things as natural forms – man, archaeopteryx, insect, animal etc – but it does mean there is no valid reason to deny them philosophically because they are immaterial (you just have to deny materialism, logically). As far as facts can determine theory, as opposed to theory’s tendency to filter facts, which Merv and I have also been discussing, the data ought to give us some guidance.

Without pretending to be initiating a serious research program, let me hint at the kind of things the acceptance of universal forms in biology might predict, which could be investigated. One might find, for example, that forms were very resistant to fundamental change, until at some point there was a quantum event and theropod reptile, for example, became bird very suddenly. This would help explain the universality of stasis followed by entirely new forms in the fossil record. Yet this would not necessarily preclude genomic change occurring in the gradual way suggested by genetic studies (and especially near-neutral change). This kind of notion was perhaps in Eldredge and Gould’s minds (following Futuyma) in reviewing punctuated equilibrium theory in 1993:

…morphological change may accumulate anywhere along the geological trajectory of the species. But unless that change be “locked up” by acquisition of reproductive isolation (that is, speciation) it cannot persist or accumulate and must be washed out during the complexity of interdigitation through time among varying populations of a species. Thus, species are not special because their origin permits a unique moment for instigating change, but because they provide the only mechanism for protecting change.

Let me give a (limited) analogy. Because I am a doctor, let us say, my library consists largely of medical texts. But for whatever reason the shelves begin to accumulate music scores, perhaps, or theological tomes, or books about evolution. Yet I remain a doctor. But at some point, some crisis occurs and I decide, or am forced, to give up medicine. Perhaps I instead become a musician, or a pastor – or worst of all, a blogger on science and faith – and the relevant accumulated information comes into its own. I may even begin to get rid of the medical books. But the library did not make me what I am – that was some different process of “speciation”, and of quite a different order to the ongoing process of filling and emptying bookshelves.

You may note that the variation in my books has relatively little to do with the “origin of the species,” though it’s clearly not irrelevant: it would be odd if my shelves had only works on the theatre in any of my incarnations. It would certainly be of interest to know why I had acquired the particular books I had ahead of a career change: would it be distinguishable from random accumulation of junk before my new status emerged?

If, in a directed theistic evolution framework, my job-change is equivalent to God’s endowment of new substantial form, the nature of the mechanisms involved are of considerable importance. Would Gould’s accelerated gradualism answer the turn? Perhaps, but so far as I can see he was, in punctuated equilbria theory, offering a mechanism of default, assuming the truth and sufficiency of Darwinian selection. Some quite different process or processes might be involved, maybe even saltational, perhaps even “miraculous” in the loose non-Thomistic sense of bypassing secondary causation.

But Darwinian nominalism it wouldn’t be.


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About Jon Garvey

Training in medicine (which was my career), social psychology and theology. Interests in most things, but especially the science-faith interface. The rest of my time, though, is spent writing, playing and recording music.
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23 Responses to More on nominalism v realism

  1. Avatar photo Merv Bitikofer says:

    Jon, thanks for continuing this series. It is a nice continuation of something you said in a prior post somewhere that I had intended to respond to at some point, and it fits here.

    I recall your implication that if a well-defined boundary doesn’t exist, then the category so defined (or not defined as it were) cannot be real —thinking of what it means to be human in an evolutionary sense where we are simply among the long continuum of life. At least that is how I understood you — please correct this as necessary.

    But I find it necessary to challenge the notion that a category can’t be real in a universal sense just because it exists in a continuum. Would we refuse to accept the reality of the color red just because it has no clear boundary as it fades into “orangeness” on one side and “infraredness” on the other? Or does your library not qualify as a bonafide library just because it started as a few books (not a library) at one time and slowly progressed to become one?

    To bring this closer to theology / humanity, we freely accept the existence of moral accountability among adults even though we cannot give a day and hour where a child becomes this morally accountable agent. The Bible gives credence to both –that there is a category of young persons who are not yet accountable, and there is certainly a category for the rest of us who most definitely are. The full objective reality of these categories is in no way threatened by a fuzzy or ill-defined (by us) boundary between the two.

    I see it as a matter of trust that God does have it sorted out even when we can’t, or even when we see some ontological continuum — that this still doesn’t defeat God’s declarations revealed about such things.

    I’ll continue this in a bit since my lunch break is ending here. More coming about science and its categories.

    • Avatar photo Jon Garvey says:

      Hi Merv

      What you describe is called (I find) the sorites paradox. Flip through that article and you’ll see philosophy’s been exercised with it for ages: is it merely a semantic thing, or a metaphysical issue (like nominalism/realism itself, really)? Taken to one extreme classification and categories become entirely worthless: frank nominalism rules.

      There’s a difference between a category with fuzzy edges and a complete continuum, I think, which is how many philosophers seem to deal with the problem: most red is truly red, but at the edges you have to hedge your bets – either you don’t know which side of the boundary you are, or it’s unknowable. Triangles, on the other hand, have clearer boundaries. Colour is a commonplace example for discussion of forms, but fraught with difficulty, it seems to me, from quantum theory to human 3-colour vision.

      Aristotle seems to have dealt with things practically in a similar way using the phrase “always or for the most part”. An essential nature might not be fully expressed (eg an infant not yet fully a man), or be defective (a microcephalic), or even be a mixture (a chimaera). And yet there is a true category “man”, which is more than a convenient semantic description.

      That I think is the key question: is there a category “man” which God creates, and treats as a specific category, eg by including its members within a covenant? Can one be given fuzzy eternal life?

      And so are there similarly natural kinds of organism, even if the boundaries might be fuzzy in various ways to us? If that were so, should we not expect to see that broadly reflected in biology, and maybe be a little more receptive to theories involving stasis and discrete speciation?

  2. Avatar photo Merv Bitikofer says:

    …thoughts continued…
    You are surely right, Jon, about the enthusiastic rush to blur distinctions and category boundaries. We see it in astronomy as we have transitioned from “Memorize these nine planets of our solar system” to instead breaking “planets” down into more descriptive categories like planetoids, gas giants, inner rocky planets. And gas giants themselves seem to merge up into a “failed/ignited star” category, though one would think the “pass/fail” options on that should remain rather cleanly binary. Anyway, the point is that additional observation seems to (more often?) complicate categorization than to solidify it.

    I do realize that this enthusiasm can then rapidly become a confirmation bias solidified into our scientific thinking habits. And I am solidly with you that a category for something so theologically important as humanity is solidly ontologically, and theologically real both across geography and across time. I speak that conviction as rooted in faith understandings more than scientific ones. If science successfully shows that many variations on hominids existed in the past that may challenge any neat Dedekindian cut I propose, then it merely reminds me that any distinctions we humans have from other animals are from God, and may or may not have been gifted to us entirely through natural causes. In any case we don’t accept exclusively natural cause as the ultimate source of anything anyway –least of all perhaps an image of God bestowed upon us.

    I’m not saying that observations about us having this discussion on the internet while chimpanzees are not doing anything remotely of the sort; –I’m not saying such observations are not valid scientific ones about our differences perhaps casting some true light on what God’s image in us means. But I’m more than a little suspicious of the program demanding that our spiritual distinctions all be spelled out in measurable terms awaiting approval from some sort of science –one of many good referees out there; but not the best one for this and many other questions.

    • Avatar photo Jon Garvey says:

      Epistemological uncertainty ought to breed humility, I agree. To deny the evidence of human solidarity that is based on common experience, on the basis of some speculations raised by projections about the past is most unwise. By which I mean that assuming there must have been a continuum of pre-human forms that must have gradually and naturally morphed into all that humanity is today is an ideological commitment rather than a scientific conclusion.

      That would be so even if there were a whole intermediate fossil series, because we’d still have no real idea of what it was like to be those creatures, nor of God’s views on the matter.

      It’s interesting, though, that there are “lumpers” and “splitters” in anthropology. Jim Kedder on BioLogos seems to be the former: he seems to see quite distinct lineages of “apes” and “man” at least biologically, rather than a gradualist continuum. It seems the evidence can be taken almost any way one likes at present.

      • Lou Jost says:

        “It seems the evidence can be taken almost any way one likes at present.”
        That is silly, Jon, except in the vacuous sense that you can always find fringe people who will hold contrarian opinions about any subject. The fossil record show a great many intermediates between the ape/man common ancestor and us. Even creationists can’t figure out which intermediates are non-human apes and which are human, strongly suggesting that the evidence favors a continuum.

        • Avatar photo Jon Garvey says:

          I disagree – Jim Kedder distinguishes pretty clearly between the genus Homo and the Australopithecines. The distinctions within those two lines have arguable significance, in terms of what we mean by “human.”

          • Avatar photo Jon Garvey says:

            And Lou, the fact you’re a splitter doesn’t alter the fact that there are many lumpers, or make them necessarily mistaken.

            • Lou Jost says:

              How did I get to be a splitter? I think you are saying “lumper” when you mean “splitter”, and vice versa.

              I was not arguing that there are no useful distinctions between these fossils, but that even creationists, who are sure there must be a clear break between apes and man, can’t consistently identify the break. This implies the break is not obvious, even to the group that is most firmly committed to its existence.

              • Avatar photo Jon Garvey says:

                Homo habilis – arboreal – some features more ape-like than Lucy. Serious proposals recently made that it be reclassified as an Australopithecine. Latter evolve slowly within pretty close limits.

                GAP (up to 1m years).

                Enter Homo erectus, with doubled cranial capacity (within modern human range), upright gait – pretty modern below the neck. Serious proposals that H erectus, H neanderthalis and H sapiens be considered sub-species of Homo sapiens. Good evidence of hybridisation between them. Cultural similarities frequent, esp between Neanderthals and moderns. Evolution on steroids in this group towards modern forms.

                I don’t pretend to draw firm conclusions from that, but Darwinian gradualism it ain’t. I like the quote from Ernst Mayr (only 10 years old and, I think, not refuted by new evidence): The earliest fossils of Homo, H rudolfensis and H erectus, are separated from Australopithecus by a large, unbridged gap. How can we explain this seeming saltation? Not having any fossils that can serve as missing links, we have to fall back on the time-honoured method of historical science, the construction of a historical narrative.”

                Were we discussing Just-so stories a while ago? I never realised the Elephant’s Child was an example of the time-honoured method of historical science. But it seems the evidence for gradualism (and indeed, for connecting Homo to Australopithecus at all) is the story told to fill the gap.

            • Lou Jost says:

              You make my point for me. First you quoted Keller’s claim that Australopithecus is clearly distinct from Homo. Then in the next comment you bring up Homo habilis and mention that taxonomists are still unsure whether it is really Homo or Australopithecus. It clearly counts as an intermediate form if taxonomists can’t easily place it in one or the other.

              Furthermore, it was bipedal when walking, and made stone tools.

              For creationists, every new fossil, instead of filling a gap, makes two new ones. Do you really want to play that game?

  3. Avatar photo Merv Bitikofer says:

    Jon, I didn’t intend to press you into an argument to persuade anybody of (at least the possibility) that significant category divisions are there to be had. Though you are free to continue to press that for Lou’s benefit as you see fit.

    But as a theist, I’m failing to appreciate any need for well-defined (by me or by any human knowledge) boundaries on an origins question for humanity. I.e. –if we were shown that there was some continuum, I fail to find that theologically threatening. My failure may be a result of philosophical ignorance on my part leading to a glib tromping through paths where smarter people delicately tread. But I think I remain open to enlightenment on that front.

    Sorite’s paradox is interesting. I start at the obvious “given” that humans and heaps do both exist and then work backwards to see what, then, must be wrong with the paradox. Vagueness of definition is as good an answer as any.

    Starting with the theological givens such as the special status for humanity from God, I am prepared to accept what comes from origins questions that science can help answer. Your reminding us of other patterns of thought (a kind of stasis around which a species may have stable identity –much like Gould’s puncuated equilibria) is a helpful alternative possibility for thinking about evolutionary science. I’ve gotta run at the moment … lunch breaks too short!

    • Avatar photo Jon Garvey says:


      I cited human origins, to be honest, only because they are a well-documented, recent, and close-to-home example of quite a dramatic evolutionary transition. The question of universals is of equal significance throughout biology (indeed, throughout nature), and that was the philosophical issue I was interested in exploring – though I need to look further, especially into how the philosophers deal with the fuzzy edges you alluded to above.

      There are, of course, particular implications for humanity, in that the development of rationality, consciousness, moral sense and spiritual awareness are undoubted changes that are difficult to view as continua, whatever the biological history looks like.

      Theologically, too, there are all kinds of questions ranging from natural law (I’m wading through some stuff on that currently – an interesting application of creation doctrine we haven’t considered here yet, not being Catholics!); the solidarity of the human race, past and present, with Christ; eternal life etc.

      If there is human exceptionality in God’s eyes, we don’t necessarily have to be able to mark out its boundaries – provided we don’t follow the route of de-humanising our fellow-humans now. Remember on the religious side the attempts to classify black races as pre-adamic non humans, and on the scientific side Haeckel’s influential claim that there was a bigger evolutionary gulf between the Australian aborigine and the European than between the aborigine and the chimpanzee. One doesn’t need to postulate separate species to place others on the wrong side of some arbitrary division in a continuum: but the existence of a universal clarifies the issue.

      The question of fossil hominins is therefore not worth meddling in with regard to what is or is not human as such – but is as significant biologically as any other taxonomical issue.

  4. Avatar photo Jon Garvey says:


    I’m out of nests in the column hierarchy (WordPress doesn’t seem to support continua), so have posted at the bottom.

    Transitionality would be one reason for the reclassification of a species, but in this case (as even the Wikipedia article on H habilis gives good indication) the issue has been doubt about the justification for the original classification into genus Homo.

    Apart from its ape-like features, some more so than Lucy, H habilis has been accused of representing a mixed assemblage of separate taxa, has been suggested on several grounds to be a separate, developed, branch from a common ancestor with Homo, and of course is known to have co-existed with H erectus for a long period in the same geographical area, as well as with Australopithecines. Even its more advanced tools can only be associated with it on the assumption that it is a more advanced transitional form so it wouild be the maker of the tools. But there were Australopithecines about too, and perhaps even “true” Homo representatives, given the rarity of any fossils.

    Habilis may well be transitional, but the fact that opinion is so sharply divided makes that transitional role just one hypothesis, which provides one more slightly loose rung in the gradualism ladder. But it would equally provide a rung for a hypothesis of relatively fine non-gradualism, given the distinctness of some of its features (eg inner ear) from both Australopithecus and Homo. And when all is said and done there is still a very big gap between even H habilis and H erectus.

    On the other hand if the skeptics are right about its place as a transitional, then Mayr is even more correct in saying that the gulf between Australopithecines and Homo looks saltational on the evidence we have. Gradualist or quantum speciation events are therefore both in the frame, and nominalist and realist viewpoints still on the table.

    What creationists may or may not say is irrelevant to the question in hand, which is about the reality of natural forms.

  5. Lou Jost says:

    Creationists have the infamous habit of seeing gaps regardless of any possible evidence. When a presumed gap is filled by a new fossil, they now note that there are still gaps on either side of that fossil. It is relevant because you are doing something similar. The fossil hominid record is getting denser and denser every decade, with more and more gaps filled in. But no finite number of fossils can possibly eliminate all gaps. You’ll always be able to find gaps where you can put your saltations (and somebody else will probably put the saltation somewhere else).

    Yet we know from genetic and karyotype evidence that humans share a simian ancestor with chimpanzees. So we expect to find intermediate forms, and we do keep finding them.

    Now it is certainly possible that there was some important mutation that gave one lineage a big advantage (like the mutation that turned on citrate use in Lenski’s bacteria). Then, this would have been refined by other mutations over time. If you want to call this a “saltation”, go ahead, but it is a normal evolutionary change.

    I do agree that some explanation may still be needed for the stasis seen in the fossil record for many species. There are interesting population genetic explanations, and these may be sufficient, bu that is still up for debate.

    • Avatar photo Jon Garvey says:

      Now that cuts both ways, Lou. If the competing theories are phyletic gradualism and quantum speciation events, then the discovery of transitional species is just that – confirmation of either theory. It is no less invalid to conclude that there must be a continuum of lost fossils between them than to assume from their absence that a continuum doesn’t exist.

      To confirm either theory you’d have to be able to observe the before and after of a clearcut speciation, and if that’s an unreasonable demand you have to stay agnostic, as one does over the meaning of stasis until someone finds a way of settling that debate finally too.

      And of course the few fossils we have only show transition at the macro-level, eg genus Australopithecus being more human-like than the supposed common ancestor with chimps, and H habilis, in some respects but not others, closer still. But even in those few specimens there are complications such as the suggestion that A africanus is a branch off the line (and maybe later than the earliest Homo specimens), and the suggestion of the importance of non-Darwinian hybridisation events (which are now confirmed between the Homo species).

  6. Lou Jost says:

    The continuous filling-in-the-gaps we have been seeing over the last century supports the overall-gradualist picture and continually refutes the placement of a major gap in any pre-specified place. But yes, you can keep moving your hypothetical gap into the spaces that will always be available on both sides of any new gap-filling fossil.

    Certainly there could have been periods of rapid evolution in this lineage, as in any other. Hybridization, too (how is that “non-Darwinian”?) But the similarities between chimp and human genomes show there were no really big quantum leaps of genetic re-organization in our lineage.

  7. Lou Jost says:

    Readers may be interested in Dennis Venema’s installment on human evolution yesterday:
    which treats some of the issues Jon and I discussed above.

    • Avatar photo Jon Garvey says:


      Do you conclude that Dennis is a nominalist or a realist?

      In fact, given that he writes for BioLogos as a theistic evolutionist, a position you fundamentally disagree with, I’d be interested to hear which of his arguments you most disagree with from all the columns you have read by him.

      • Lou Jost says:

        I don’t think a biologist can be pigeonholed into one those two categories. As I mentioned in earlier comments, lines between species are sometimes meaningless and arbitrary, especially when we are looking at a single population over time, but are often sharp and meaningful when two formerly-conspecific populations diverge and achieve reproductive isolation.

        I generally agree with Dennis’ posts. They are straightforward, accurate, well-written introductions to evolutionary topics.

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