The experience with which the sciences of human action have to deal is always an experience of complex phenomena…. We are never in a position to observe the change in one element only, all other conditions of the event remaining unchanged. Historical experience as an experience of complex phenomena does not provide us with facts in the sense in which the natural sciences employ this term to signify isolated events tested in experiments. The information conveyed by historical experience cannot be used as building material for the construction of theories and the prediction of future events. Every historical experience is open to various interpretations, and is in fact interpreted in different ways.
The data never, ever ‘speak for themselves.’ Theory is always required to make sense of data – indeed, of reality. Therefore, people who are poor theorists are never to be trusted to make sense of reality regardless of their facility with collecting and processing data.