Sometimes, late at night, when the branches of the large pine outside my window are swaying in a hot breeze and brushing with a sinister whisper against my window panes, and sleep seems to loom far above me like some inaccessible peak floating in the cerulean depths of the Himalayan sky, I find myself worrying obsessively about the thylacine and the fossa. What accounts for them? Are they perhaps signs of some cosmic mystery that the sciences will ultimately prove impotent to penetrate? Are they quadrupedal portents of the transcendent? Or are they signs of a physical determinism so absolute as to be indistinguishable from fate?

If you are not given to similar anxieties, however, you may not know what I am talking about. So maybe I should try to explain what I mean.

The great danger that bedevils any powerful heuristic or interpretive discipline is the tendency to mistake method for ontology, and so to mistake a partial perspective on particular truths for a comprehensive vision of truth as such. In the modern world, this is an especially pronounced danger in the sciences, largely because of the exaggerated reverence scientists enjoy in the popular imagination, and also largely because of the incapacity of many in the scientific establishment to distinguish between scientific rigor and materialist ideology (or, better, materialist metaphysics).

This has two disagreeable results (well, actually, far more than two, but two that are relevant here): The lunatic self-assurance with which some scientists imagine that their training in, say, physics or zoology has somehow equipped them to address philosophical questions whose terms they have never even begun to master; and the inability of many scientists to recognize realities”even very obvious realities”that lie logically outside the reach of the methods their disciplines employ. The best example of the latter, I suppose, would be the inability of certain contemporary champions of “naturalism” to grasp that the question of existence is qualitatively infinitely distinct from the question of how one physical reality arises from another (for, inasmuch as physics can explore only the physical, and the physical by definition already exists, then existence as such is always “metaphysical,” or even “hyperphysical””which is to say, “supernatural.”)

But that is all matter for another time. Here I do not want to argue about being. I have, rather, a very simple worry to confess about the competence of method”any method”to recognize its own boundaries. All method, after all, as the etymology of the word exquisitely shows, is an elective practice of cleaving to a particular path ( met’-hodos ), a labor of limiting oneself to a particular approach to a problem in order to achieve as precise an understanding of that problem as may be achieved from one perspective. But that means that method always remains only a perspective, however powerful it may be: a willful blindness to many things for the sake of seeing a few things with a special clarity. A man peering into a microscope has been vouchsafed a glimpse into realities that the naked eye could never see, but he may also fail to notice the large fire that has just started on the far side of his laboratory, near the only exit.

Modern experimental science began to coalesce into a general method with the rise of the mechanical philosophy and the shattering of the old Aristotelian fourfold structure of causality. That may be only an accident of history, in long retrospect; but, whatever the case, the magnificent force and fecundity of modern scientific method is in part the consequence of a conscious decision to eschew any explanation for any physical phenomenon that requires the invocation of final or formal causes. By thus prescinding from teleology and causative morphology, experimental science was allowed to devote itself unwaveringly to those material and efficient processes at work within any physical event (though here “material” and “efficient” no longer have the meaning they had in Aristotelian thought). In Daniel Dennett’s language, science learned to think in terms of “cranes” only, and entirely to discount the possibility of “sky-hooks.”

Even so, it would be worse than naïve to imagine that the sciences have thereby proved the nonexistence of final and formal causes. In fact, by bracketing such causes out of consideration, scientific method also rendered itself incapable of pronouncing upon any reality such causes might or might not explain. Now, of course, the typical reply to this observation (from the aforementioned Daniel Dennett, for instance) is to say, with some indignation, that modern science has in fact demonstrated the utter superfluity of final and formal causal explanations, because the sciences have shown that they do not need finality or formality to understand the processes they investigate.

That, however, is an empty tautology: Of course modern scientific method discovers the kind of reality it is specifically designed to discover; and even in cases where it finds its explanatory reserves overly taxed, it must presume that in future some sort of “mechanical” cause will be found to restore the balance, and so issue itself a promissory note to that effect. But, again, this may mean that it must also overlook realities that actually lie very near at hand, either quite open to investigation if another method could be found, or so obviously beyond investigation as to mark out the limits of scientific method with particular clarity.

Which brings me to the thylacine and the fossa.

The thylacine, if you do not know, was an apex predator once found in Australia, Tasmania, and New Guinea, of which some old film footage still exists, but which was rendered extinct some time last century. It was, for want of a better term, a marsupial wolf. Though only at most very distantly related, by very remote extraction, from some of the same ancestors as the placental mammalian canines of other lands, its skeletal shape, its behaviors, its movements, and so on were remarkably lupine. The fossa is another predator, happily not extinct”not yet, at any rate”and is an inhabitant of Madagascar. It is a viverrid (probably), a distant cousin of the mongoose, but it has a large number of felid traits; that is, it moves, hunts, and to a real degree looks like a cat, inside and out.

Now, I have heard evolutionary biologists speak about both animals on more than one occasion, and the usual explanations adduced for either animal’s morphological resemblance to species far removed from its own are drawn, to varying degrees, from genetics and convergent evolutionary theory. There are similar codes embedded deep in the labyrinths of the genetic material that thylacines and wolves, or fossas and cats, inherited from some amazingly ancient common ancestors. Or similar environmental pressures were exerted on the evolutionary processes of all the creatures involved, resulting in some very similar morphologies. Or both, really.

I am not qualified to pronounce on these things, though I have two melancholic molecular biologist friends who become vague and evasive when I raise the issue with them. One worries that, as the “classical conception of the gene” has begun to fall apart in recent decades, and the idea of genetics as a science of information flow, analogous to the reading of software programs, has been challenged by a more indeterministic view of genetic material, it is not exactly clear how genetic coding could prove so cohesive and unidirectional over such vast epochs. Organisms, he tells me, as systems, use genetic material in such various ways that “there is no such thing as a ‘gene for’ this or that.” So it would take some considerable run of improbable coincidences for two complex systems to evolve separately while employing the same material in such similar fashion.

The other approvingly quotes Gould’s famous assertion that, if the tape of life were wound back again to the time of the Burgess Shale and allowed to play forward again, it would arrive at totally different results. The notion that there is evolutionary convergence in certain details of physical development across species divisions”the shape of a wing, the mechanism of a cameral eye”makes good sense to him, but the independent full development of close morphological analogues like the timber wolf and the thylacine seems to strain his credulity. If evolution is a sort of “algorithmic” process of chance mutations, incredibly numerous and rare and unpredictable, selected by adventitious environmental conditions, and is a process moreover whose course is cumulative but not accumulative”progressive but not directed”then it is certainly surprising that genetic variation over millions of years under varying conditions in different regions could actually produce such similar results in such complex organic structures.

Not that either man suggests that the working theories are wrong. And I, for what it is worth, have no opinion in the matter whatsoever. I am not qualified to have an opinion. It simply strikes me as pleasing to imagine supplementing (or even underpinning) the genetic and the convergent explanations with the Platonic or Aristotelian suggestion that, perhaps, there is such a thing as the form of the wolf or the form of the cat”lupinity or felinity as such”that impresses itself upon the somewhat intractable material substrate according to the prevailing conditions in a given time or place. Then the existence of both a placental mammalian wolf and a marsupial wolf, born at the end of evolutionary genealogies separated by oceans for millions of years, seems hardly surprising at all. If nothing else, this notion is not much more incredible than the idea that there is, say, a sort of cat-shaped niche out there in certain ecosystems that environmental forces will inevitably cause to be filled. (Then again, maybe it all has something to do with the Great Chain of Being.)

That, however, is also not my point. I have no doubt that evolutionary biology has much to say, and will continue to find more to say, regarding these strange symmetries across discontinuities in the lineages of living things. My question really is one regarding method. If there were a case in which modern biological method came up against a reality that seemed to point towards orders of causality it could not logically investigate without altering its working premises radically, would it be able to recognize that it had reached its limit? Could it admit as much to itself, or tell us about it? It is an imprecise question, so open as perhaps to be vacuous, but I raise it just the same, because only when a method is conscious of what it cannot explain can it maintain a clear distinction between the knowledge it secures and the ideology it obeys.

David Bentley Hart is contributing editor of First Things . His most recent book is Atheist Delusions: The Christian Revolution and Its Fashionable Enemies (Yale University Press). His other “On the Square” articles can be found here .

Author’s Note: This will be my final column On The Square. Beginning next year, I shall instead be contributing a regular column to the print edition of First Things (though I may make the occasional irregular contribution here). My sincere thanks to regular readers of these web-offerings (is that a proper term?), both friendly and hostile.

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