Continuing on the subject of the history of the strengths philosophy, if you haven't read Managing Oneself, Peter Drucker's seminal work on the subject, written for the Harvard Business Review in 1999, I suggest you do so. How about this to whet the appetite:
Most people think they know what they are good at. They are usually wrong. More often, people know what they are not good at - and even then more people are wrong than right. And yet, a person can perform only from strength. One cannot build performance on weaknesses, let alone on something one cannot do at all.