 Solution

The history of science is relevant because a philosophical account purporting to describe scientific knowledge and rational change must fit more than the finished derivations in current textbooks. Historical episodes reveal what evidence was available, which alternatives were considered and how assumptions about instruments and phenomena were revised. A reconstruction that imports later knowledge can make a reasonable contemporary choice appear irrational.

A simple picture of falsificationism illustrates the point. A discrepancy between an observed orbit and a calculation need not immediately discredit Newtonian mechanics. The prediction also uses estimated masses, initial data and assumptions about other bodies. Investigating an additional perturbation may be more informative than rejecting the entire theory. History can show whether such a proposal was independently constrained and successful, rather than merely a device for avoiding any possible refutation. The philosophical distinction between a testable extension and an ad hoc hypothesis therefore benefits from examining actual evidence and practice.

Thomas Kuhn's introduction to The Structure of Scientific Revolutions by Thomas Kuhn challenges the picture obtained from retrospective textbook accumulation. His distinction between normal science and revolutionary theory change directs attention to changing research problems, standards and exemplars.^[ref] Whether one accepts that particular account, the historical challenge is substantive: an account of progress must explain why some earlier achievements remain useful while broader frameworks change.

Historical explanation is not itself a complete justification. Showing that a social setting or personal commitment caused someone to accept a theory does not show that the theory was well supported. Nor does a single episode automatically refute a normative ideal: actual scientists can make mistakes. The context of discovery and context of justification can be distinguished even when they interact. What matters is identifying the standard being evaluated and the evidence relevant to it.

History is therefore neither dispensable decoration nor an infallible rulebook. It can expose counterexamples to oversimple universal claims, supply scientifically realistic cases and reveal unnoticed alternatives. Philosophical reasoning must then assess the inference, the evidential situation and the claimed norm. A good account should be historically responsible without reducing rational justification to whatever scientists happened to do.