Creations, new insights, and paradigm shifts emerge at junctures where different theories – different world views – meet, come in conflict, and are forced to accommodate. So it can be with a theory of expertise and a theory of human intelligence. Over the course of 20th-century research, the developments of these two “world views” have run along separately, rather like Leibnitz's clocks, each addressing much the same question – what are the major capabilities of the human and how do they come about – but neither speaking to the other. They have arrived at different conclusions, neither thoroughly correct, of course, but neither entirely wrong either. Now, we reason, if we put the two theories in newly-met dialog, we can drive off the odious irrelevancies of each in a distillation that captures the truthful essence of both – a new liquor: a theory that is more accurate than any that has gone before. That, immodestly, is what we present in what follows.

We deal with the question of how expertise fits within that part of human personality we describe with a theory of human intelligence. Thus, the larger perspective is that of personality – a theory that describes what people do and explains why they do it. The principal descriptive concept of this theory is behavioral trait, a characteristic that persistently distinguishes one individual from another despite variation in the circumstances in which individuals are found.