There is an unbridgeable gap between the experience of a person’s mind and the circumstances external to the mind. Laughs, tears, heart rates, neural firings, and so on are not the mind’s experience. Since the mind’s experience cannot be quantified, no quantitative correlation can exist between the mind’s experience and circumstances external to the mind.
It is possible, however, to make judgments concerning the magnitude of effects (even though they are non-quantifiable theoretically). Such is the procedure of history, as opposed to theory.
Take a look at Mises’s book, Theory and History, for a discussion of the distinction: