As I have argued before, there is a class of objects in the biological domain that do not derive from the theory of that domain, but which are in fact the special objects of the domain that call for a theoretical explanation. The example I have given is mountain, which is a phenomenal object of geology, and yet not required by the ontology of any geological theory, which does include overfolds, tectonic plates, upthrusts, the process of differential erosion, and so on. At the end of the theoretical explanation, the mountains have not disappeared so that we might now drive from Arizona to Los Angeles on the flat, but they are fully accounted for.
Much ontology in special sciences is of this kind: listing phenomenal objects. Sometimes a phenomenal object is something that is merely salient to us as organisms. Mountains are things we must navigate over or around. They have a more than epistemic status. They are, in this case literally, a distribution of measurements (of elevation in this case). The measurements are objective in the sense that any measuring device properly calibrated will give the same results for any observer. I will call this assay objectivity – a phenomenon is assayable in a fashion that is not subjective. I do not say there is a mountain there because it seems to me there is. I say there is a mountain there because there damned well is, and anyone who want to deny it had better be able to account for their elevation when the rest of us say they are at the peak.
There are, famously, other senses of phenomenality that can be constructed in ways that are culturally relative, or subjective (note: subjectivity and relativity are not the same). Infamously, some phenomenal objects are entirely constructed by observers, like… well it’s actually hard to come up with examples. Even in cases like “race” there are underlying distributions of assayable data – the moreso in these days of geographical distributions of alleles. Race may be a construct, but it is not a construct with only political underpinnings; there really are differences in, say, resistance to malaria and susceptibility to sickle cell anemia. Perhaps the difference between Catholics and Protestants is a pure construct, but it is not, so far as we can tell, a difference we ascribe to biology (now) anyway. [To head off the obvious objections: I do not believe races exist in the human species, as by the usual criteria for races in biology humans lack the requisite variation; our "races" are political, social, geographic and phenotypic constructs based on actual but fairly shallow differences. A single troop of chimps has more genetic variation than the whole human race (can anyone find the citation for that claim, by the way?). There are differences, but not persistent or deep enough to warrant calling these groups races.]
Phenomenal objects are in effect specified by the prior existence of the special domain in which they are recognised. If you have a domain “biology”, then objects that routinely appear in that domain, like “organisms”, are specified as objects of that domain. In an extreme reductionist approach, in which everything is physics, this is tantamount to saying “some physical systems get called organisms”. That is, these are just another way in which physics plays out. Like black holes, G class stars, and, yes, mountains, they aren’t “really” objects of a special domain. So on a strong reductionist view, one ought to deny that these phenomenal objects are, in fact, special objects of the domain at all. Of course, a strong reductionist approach says the same thing about theoretical objects as well.
The conundrum we have is this: if we do not want the phenomena to simply be arbitrary and instrumental artifacts of our limited epistemic capacities, if we don’t want these things to be “real” just so far as we cannot make the proper inferences from physics to organisms, etc., we need some reason to think the domain is a domain apart from a mere implementation of physics. Or is Rutherford right when is said “In science, there is only physics. All else is stamp collecting”? How can we be physicalists and not merely stamp collectors in biology?
One way is emergentism. This is the view that there are properties at some levels that, while they involve physical objects and only physical objects, arise at a level of complexity. These properties are said to be emergent properties. There are several versions [pdf] of emergentism – the one I am interested in here is systemic emergentism, which Stephan in the previous link defines thus:
Emergent properties are systemic properties. A property is a systemic property if and only if a system possesses it, but no part of the system possesses it.
The important features is that the property must be a system property, which implies for any domain that there are systems in that domain, and that a simple physical enumeration of all the parts of that system will not give you the property. So we have a couple of implications. First, there is a system class in the domain (e.g., organism), and second that there are properties of that system that are not properties of the components which it or any other system of the same class comprise.
Having system properties, however, might be something fairly innocuous for a reductionist. They might be simple epiphenomena – properties that are merely formal and have no causal power. I think we can assume that we want our properties to be causal, and on a reductionist account like Rosenberg’s, these system properties are not, in the final analysis, causal. That is, there is no downward causation, from one higher level to the lower level. An example might be that there is no system property that makes molecules of nucleotides recombine when an egg of a vertebrate is fertilised. All the causation happens at the physical level. Actually, I should scare quote “physical level” here; if we assert there is a single physical level we are begging the question in favour of reductionism.
The problem I have with emergentism is that is, too, resolves in my view, to epistemic properties. To explain this I should use a physical example – a case in which some property was thought to emerge at the “physical level” from physical component properties – water. You’ll find this in Mill’s System of Logic (Bk I, ch VI). After suggesting that we can inductively infer the properties of objects from their components, he says (p426ff):
This principle however by no means prevails in all departments of the field of nature. The chemical combination of two substances produces as, is well known, a third substance with properties entirely different from those of either of the two substances separately, or of both of them taken together. Not a trace of the properties of hydrogen or of oxygen is observable in those of their compound, water. The taste of sugar of lead is not the sum of the tastes of its component elements acetic acid and lead or its oxide; nor is the colour of green vitriol a mixture of the colours of sulphuric acid and copper. This explains why mechanics is a deductive or demonstrative science, and chemistry not. In the one we can compute the effects of all combinations of causes, whether real or hypothetical, from the laws which we know to govern those causes when acting separately; because they continue to observe the same laws when in combination, which they observed when separate: whatever would have happened in consequence of each cause taken by itself, happens when they are together and we have only to cast up the results. Not so in the phenomena which are the peculiar subject of the science of chemistry. There, most of the uniformities to which the causes conformed when separate, cease altogether when they are conjoined; and we are not, at least in the present state of our knowledge, able to foresee what result will follow from any new combination, until we have tried it by specific experiment.
Or so it stood in 1843. Now, not only can we predict the general properties of water from a knowledge of the properties of elements, and in fact the particular microstructural properties of water in special cases – why there is a structure in cells and water in containers, etc. What changed? Well, obviously the valency theory of elements is the major change, but even then Mill might have said we cannot make the predictions. The real (or actually “unreal”) change here lies in the rapid expansion of our own computational abilities. We now have computers that can predict the behaviour of water at the microlevel, and thus the overall “liquidity” that had remained imponderable in Mill’s time, and for thousands of years prior to him.
So at some point, our computational capacities make the shift from “inferable” and “predictable” to “emergent” and “unpredictable”. Emergence is thus, in my view, a matter of what information theorists call “surprisal” – which is a measure of the expected observation compared to the actual observation. An emergent property is one that surprises us, in short. This means it doesn’t solve our problem, for it is a matter of epistemic limitations, not ontology.
Incidentally Mill goes on to make an explicit link to biology – the term “organised bodies” here is a previous term in common use before “organism” was introduced into English from the French:
If this be true of chemical combinations, it is still more true of those far more complex combinations of elements which constitute organised bodies; and in which those extraordinary new uniformities arise, which are called the laws of life. All organised bodies are composed of parts, similar to those composing inorganic nature, and which have even themselves existed in an inorganic state; but the phenomena of life, which result from the juxtaposition of those parts in a certain manner, bear no analogy to any of the effects which would be produced by the action of the component substances considered as mere physical agents. To whatever degree we might imagine our knowledge of the properties of the several ingredients of a living body to be extended and perfected, it is certain that no mere summing up of the separate actions of those elements will ever amount to the action of the living body itself.
It is not so certain in 2008. This must give us pause when we try to consider a priori what is and what is not explicable in terms of physical components. And the explanations we give now are causal at the physical “level” (that is, in terms of molecules, and physical forces like the Strong and the Weak force, and van der Waals forces). So I reject emergentism as a solution.
A variation on emergentism is holism, in which there just are properties of wholes, and they are irreducible. A view closely associated with Arthur Koestler, I believe this is – like the vitalism with which is it closely related – a dead issue. It is very popular amongst mystics and theologians, but not so much amongst scientists, although often views get called holistic which are just instrumentalisms, which make of epistemic necessity, ontological virtues. “Whole organism” biologists need not be holists, so long as they understand what they are protecting is the instrumental value of studying things at one scale of description because (as we saw for emergent properties) it is a limitation of our cognitive capacities that we cannot start at the “bottom” and work up.
So we seem not to have a solution for reductionism. If a domain is phenomenally salient, and the resultant science is special just because it serves us to study it, it looks like we don’t have an ontology for the special sciences. So what do we say? I think we just suck it up and say that an ontology need not be irreducible. We do have a domain of biology; if it is just a phenomenal domain, in which all its laws or generalisations are reducible to physics, so what? We now need a science of biology. We now need a science of geology, and other historical sciences, and while they may all one day be easily reducible to physics (I doubt it) they aren’t now. So we are entitled to say that biology contains organisms and other objects, only some of which are derivable from theories of biology.
This also means we should not worry too much that we have no exceptionless laws of biology that are not laws of physics. Not every science need be physics all the time We still want to know about the biological realm (and all those other special science domains). It may be stamp collecting to a theoretical physicist, but it is very interesting stamp collecting. It is not trivial to discover how a species of organism behaves in an environment. Nor is it trivial to discover how a particular kinase sets off a signal cascade that results in the death of an otherwise healthy cell, and so on. These are interesting phenomena and explanations. This is an increase in our knowledge. So screw the physicists. They are to be appealed to only when it helps us understand biology (if you are biocentric as I am). Otherwise, they can go argue over string theory, while biologists get to the business of understanding the macroworld around them.