Prediction or Explanation?

A couple weeks ago political scientist Jacqueline Stevens attacked her own discipline on the opinion pages of the New York Times. Her critique, as portrayed in the piece’s title, was that political scientists are “lousy forecasters.”

Many political scientists have responded to Stevens’ piece, from different angles and levels of rage, but one theme I’ve noticed is people disputing the assumption that political science’s goal is to make forecasts. For example, this recent letter to the editor of the Times by a professor emeritus of political science at the University of Iowa:

Forecasting is a very specialized field in political science, limited to predicting election outcomes, and the record in that field is impressive. But that is not what most political scientists do.

Political science, like most social sciences, seeks explanation rather than prediction. Its aim is to explain puzzling phenomena by relating them to phenomena that are well understood. Much of science consists of trying to resolve puzzles in that way.

I actually think prediction is what the majority of political scientists do. The distinction is that Stevens focuses on a couple of extraordinary historical cases, whereas most political science predictions involve more specific data sets. For example, theory might say that when we apply experimental treatment X, Y will increase or decrease. Or, someone might claim that Republicans give more to charity than Democrats, which is a prediction about what a data set of party identification and giving behavior would reveal.

It’s hard for me, in contrast, to think of a political science example of explanation that is divorced from prediction. I suppose the idea is to find a historical case–let’s take Stevens’ case of the end of the Cold War–and try to predict it retrospectively. But then why wouldn’t the prediction there apply to any future situations–why wouldn’t it also be a forecast? If the idea is that every historical case has to be considered on its own and that as a result their explanations tells us nothing about the future, I don’t know if that is science at all.

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