volcano

Evolutionary biologists and geologists speak of events happening millions or billions of years ago as concrete facts. They are not observational facts, though; they are inferences from indirect evidence. Indirect evidence can often lead to different conclusions; in fact, some philosophers like Duhem and Quine argue for “under-determination of theory by data,” meaning that data can never converge to support just one theory. Some can demonstrate logically that there are an infinite number of theories that can explain a set of data. Evolutionary scientists counter that there are only one or a few that are reasonable (implying that theirs is among the limited set of reasonable ones). Recent discoveries that threaten to overturn past reasonable theories, though, cast doubt on their confidence.