Recently there has been a storm of debate over what difference, if any, exists between historical and observational science. Unfortunately, those championing the idea of there being a difference between the two also have the ulterior motive of wanting to supplant rigorously tested ideas with their brand of dogmatism. As a consequence, the public response has been to reject the notion of there being any kind of divide, which effectively amounts to pouring out the champagne with the cork. Brushing aside fanatical opposition, it is important from the perspective of the philosophy of science to explore these two kinds of science.

In observational science, we have data pertaining to the actual events in question. 1 These data serve as the conditions for exploring various models, which we can then falsify by generating testable predictions about the world.

I show you a coin. I flip it for you many times, recording the sequence of heads and tails. You may then build a model using these observations to declare whether the coin is fair or biased.

In historical science, we do not have data pertaining to the actual events. We only have data pertaining to the aftermath of the events. Therefore we need to discover a set of initial conditions that, when applied to the correct model, give us the present state. But there may be many competing models and initial states, and so it is not necessarily possible to state with certainty which events actually occurred.

A given model and set of conditions that are capable of predicting the present state may be sufficient but not necessary to produce the present state. To assert otherwise would be affirming the consequent.

My lawn is wet. I know from observational science that rain and sprinklers alike are sufficient for producing this behavior. I can observe each of these in action to cause my lawn to become wet. Both conditions are sufficient for my lawn being wet, but only one of them actually occurred. Can you tell me with confidence which actually caused my lawn to be wet?

The models discovered by observational science are essential when doing historical science; indeed, that is the only way to do historical science! The methods employed by Ken Ham et alia that inspired this debate in the first place are, in my opinion and, as has been seen, in the opinion of the mass public alike, very much invalid. However, it is important to acknowledge while the conclusions they drew may not follow from the premises, the premises themselves aren’t necessarily suspect.

Regular science encompasses both observational and historical science, and more often than not, they depend on each other in order to make progress. Moreover, it is not clear whether any discipline ever engages in one exclusively without ever engaging in the other. It is more likely that most activities of normal science lie in a continuum between the two. Importantly, the burden of scientific proof is still required when dealing with both kinds of science — otherwise they wouldn’t be science, now would they?

In summary: in observational science, we have the initial conditions and we seek to find the right model. In historical science, we supply the model and we seek to find the right initial conditions. On the basis of these definitions, I believe they are closely related but different types of scientific activity.

Further reading: Cleland, Carol E. “Historical science, experimental science, and the scientific method.” Geology 29.11 (2001): 987-990.