Thanks! I love the Enneagram! And yes, it has been criticized for not holding up to sicentific rigor in empirical studies. I think that is primarily becasue of both its complexity and layering as well as the multi-faceted nature of personality itself. Also, from my own experience, some of the most effective tools in real clinical work with real people do not fare well in empirical studies. Our experimental research process necessitates that we "isolate variables" - with good reason, of course. But to me, that flies in the face of human behavior that is so nuanced and interdependent - the old "whole is greater than the sum of its parts." Our experiements make us separate the parts and while this leads to some insights, I beleive it dilutes others.

I hadn't heard of that book, but will definitely look it up. And your article as well!