Published online by Cambridge University Press: 28 February 2022
Scriven, with his well-known bridge example, showed that explanations need not carry with them accurate or useful predictions. A bridge has collapsed, but there is no history of overload or natural shock. Metal samples taken near the break show severely reduced elastic capabilities of a sort usually associated with natural aging. Therefore, given that the bridge did fall, it fell because of this sort of metal fatigue. However, on the basis of current theoretical and measurement capabilities, it could not have been predicted that it would fall. (Scriven 1962, pp. 181-185).
The existence of explanations which lack true or even usefully approximate predictions is not restricted to complex situations in engineering. Nor are such explanations the exclusive property of the non-physical sciences. The existence of such explanations, I want to claim, is common in the physical sciences as well.