Saving the Date vs. Coherence Reflections on fossils and scientific method

Saving the Data When Copernicus’ proposal that the planets all orbit the sun was put forward a narrow interpretation of his system was proposed: That all his account was meant to do was to fit the data, that is, to correctly predict the motions of the planets through the night sky.

Galileo It was Galileo’s insistence that the Copernican theory was literally true that led to his encounter with the inquisition and his subsequent imprisonment. So we have a long history of two very different attitudes towards scientific theories: according to some, all that they are meant to do is to fit the observable facts; according to others, though, scientific theories actually aim to tell us the truth about how things are in the world.

Upshot Of course in the case of Copernicanism, we’ve become convinced in the meanwhile that Copernicus was really right– that the planets do move around the sun, and not around the earth, as Ptolemaic astronomy held. But today only Copernicanism and its successor, Classical (Newtonian) physics really fits all the observable data concerning the planets’ motions. (In fact, some of the data requires refinements to Classical physics found in Einstein’s theory of general relativity.)

So the question remains: Which view of science is right? Does science just aim to ‘save the data’? Or does science aim to describe the world as it truly is?

A Different Question What are the data that we need to ‘save’? Is saving the data (fitting all of our observations into the scientific ‘picture’ of things) really all that we ask of a theory? Is saving the data the same thing as coherence, such as the coherence between claims about processes and traces that underwrites knowledge of the past?

An unkind example If the data really are just the presently observable facts, then the 5-minute hypothesis fits the data just fine. But no scientist would take that hypothesis seriously as a scientific proposal! Why not? After all, by hypothesis, it does save the data! What’s wrong with the 5-minute hypothesis?

Coherence Fitting the data is part of what coherence demands. If we have data, i.e. claims that are well-established by observation, any correct theory has got to be compatible with them. But coherence has a more positive side: to be coherent, a theory needs to do more than fit the data.

What more? It must explain at least some aspects of the data– that is, it must provide enough information about the circumstances that we can infer (some of) what we observe from other things that we observe. It must make predictions about other data we might observe. (This is pretty well guaranteed give the explanatory requirement.) Some of these predictions must be observed to be correct. (This sort of successful application of a theory is sometimes called vindication.)

Consider Fossils

Does the standard view of fossils have coherence? We have explanations of many features (the bias towards fossils of hard parts, the kinds of rock where fossils of various kinds are found, etc.) We also have applications (we can make predictions about what sorts of fossils should be found in what rock formations) that have succeeded, i.e. we have vindication. So the answer is, yes, indeed– and increasingly so, over the course of history since Steno and Hooke.

How does the 5-minute Hypothesis deal with fossils? It says that the world as we now observe it is just as if it was the result of a long history of geological and biological processes, with all the ‘traces’ such processes would leave. But they aren’t traces of processes that really happened. They are ‘as if’ traces of processes that never happened.

The Coherence of the 5-minute hypothesis Whether we think the 5-minute hypothesis meets our conditions for coherence depends on how we think of it: We can think of it as including the entire normal scientific story, all under the dismissive qualification that things are ‘as if’ all this were true. Then it is just as coherent and just as testable as the normal scientific story. But it’s also hard to tell the difference between the two: Just what does adding ‘it’s as if’ to the front of everything scientists say really do? Does this ‘it’s as if’ really mean anything at all?

Parasitic Theories A parasitic theory is a theory that uses a different, underlying theory to ‘do all the work’, and then (pretends to) reject that theory and present an alternative to it. But if all the work is done by the underlying theory, then we have to ask why we should take the ‘success’ of the parasitic theory as a reason to take it, instead of the underlying theory, seriously. For scientific purposes, the parasitic version of the 5 minute hypothesis is indistinguishable from the standard view. The phrase, ‘it’s as if,’ adds nothing at all and so (we might argue) should not be regarded as meaningful at all. (Only a kind of ‘conceptual momentum,’ deriving from its standard use in cases where it really makes a difference, leads it to seem at all significant here…)