Experiments Are Not Necessarily Designed To Be Like Particular Targets

To the extent that Guala’s and Morgan’s attribution of superior inferential power to experiments rests on their being designed to correspond materially to predetermined targets in the world, this account has a problem. Experiments are not always designed this way. Experimenters do not always go in to their experiments with a clear idea of what their targets in the world are “made of,” for at least two kinds of reasons: (1) they do not

have a particular target in mind at all,23 _{because they focus initially only on designing a} particular sort of experimental system and have not yet decided or figured out what kinds of inferences to the outside world they will draw from it, or (2) they have a particular target in mind but have minimal knowledge of its properties. I will discuss both of these reasons in turn.

One kind of case where experimenters do not know what their target is made of is when they do not have a concrete target outside of the experimental system in mind when they design the experiment. Many, perhaps even most, experiments are designed to

answer a particular question about the world, and thus designed with a particular target in mind to tell us something about. This is certainly true of the economics examples Morgan discusses. But this need not be the case; the paradigm examples of exploratory

experiments discussed in Chapter 3 are cases in point. Sometimes an experimenter’s goal is to design an experimental system, study it, and see what happens, or to collect as many data as possible and then figure out how to interpret them and what we can learn from them. The Lenski experiment, while not a paradigm case of exploratory experiment, is another example of an experiment designed without a specific target in mind. The experiment was designed to create an object of study which would offer new kinds of insight on the dynamics of long-term evolution. Its design was driven by evolutionary theory, but it was not designed to test a single hypothesis about the world that came from that body of theory, and it was not designed with a particular target in mind that it was

23 _{I should underline that I am using ‘target’ here, as I do throughout the dissertation, to mean the system of}

study in the natural world about which it is a researcher’s ultimate goal to learn or infer something. When I say they do not have a particular target in mind I mean just that they do not have a particular system fitting this description in mind—not that they have no target in mind in the colloquial sense of the term, that is, that they have no aim.

supposed to tell us something about.24 _{Intended routes of inference about the natural} world were not built into the experimental setup from the getgo, as Guala says (and Morgan sometimes implies) is a universal feature of how experiments are designed. These came after the system was designed and its dynamics observed over time.

A second kind of case where experimenters do not know in advance what the target is “made of” is when they have no empirical access to it in principle. This is usually not the case in biology, where the targets of interest are natural populations of organisms and their evolutionary trajectories, which we can observe to varying degrees. But in certain sorts of cases experiments aimed at filling in our understanding of long-ago evolutionary history have this feature. An example of this is research on the origin of life. One key aim of experimental work on the origin of life is to demonstrate how certain processes, like spontaneous formation of lipid bilayer cell walls or the encapsulation of information-carrying molecules therein, can take place and therefore might have taken place approximately four billion years ago in the prebiotic soup. The target itself (the set of events, entities, and processes involved in the actual origin of life on Earth) is empirically inaccessible to us for obvious reasons. So the aim of creating trustworthy experimental systems here cannot be to make them as much as possible like the target, in the same way we might think of making a scenario in an economics lab as much as possible like real market dynamics in the world. Rather, the aim is to set up an experimental system, using

24 _{What exactly is the target, then? It seems too broad to say that the target of the Lenski experiment is the}

set of all past, present, and future entities subject to evolutionary processes. Likewise, it seems too narrow to say it is the set of all E. coli in the world (just because E. coli happen to be the organisms in the experimental system) or the set of all bacteria, asexual organisms, etc. The experiment was designed to inform us about evolutionary processes, and the laboratory organisms were chosen for their virtues as experimental subjects, as discussed in Chapter 2, not because they have some special correspondence to a given set of organisms in the world designated as future targets of inference. It makes sense to think about the targets of the Lenski experiment only in the context of particular claims which are made about the world, for example, macroevolutionary trends in the fossil record or pathogenic E. coli populations outside of the lab, in the punctuated evolution and high mutation rates discussed in Chapter 2, respectively.

the best theoretical knowledge available, which we have reason to think might teach us something about how the target might have been. This same sort of point is true of the historical sciences in general.

I raise these considerations just to point out that judgments about inferential power should not be grounded in experiments being explicitly designed to be “made of the same stuff” as their targets, or to capture aspects of a predetermined and well- characterized portion of the outside world in their material constitution, as Guala and Morgan imply. Inferences about targets in the natural world can be thought of after the experiment has been designed, even after it has been carried out. This is an objection to the way Guala and Morgan talk about the process of experimental inquiry, but it is not really a severe point against the materiality thesis. It is more a point about timing than about material correspondence or lack thereof, per se. My response in the following subsection presents a more serious challenge to the view that material object–target correspondence confers superior epistemic power on experiments.