Recently I’ve been feeling more drawn to the enneagram, and more inclined to read and post in the enneagram forum on here than the MBTI forums. I prefer the enneagram to the cognitive functions, but I think in many ways, the MBTI letters/dichotomies/preferences make for a better theory than the enneagram. The MBTI preferences have more scientific support than either the functions or the enneagram, and also correlate to four of the big five factors. Unlike the functions or the enneagram, we can know that the MBTI types, as derived from the preferences, exhaust all the possibilities, so long as they are taken as continuous dimensions rather than black and white dichotomies. So, for example, as I use the theory, saying that someone is an ISTJ just means that person is more I than E, more S than N, more T than F and more J than P. In each case, that could be anything from very slightly more, just barely beyond the middle, to being out at the extreme end of the continuum. If the person is truly in the middle on any of the dimensions, an X can be used to designate that, e.g. ISXJ. I know that’s not exactly how the official MBTI folks use the theory, but I think it’s the most sensible way to use it. Still, I think the enneagram has got at some things the MBTI has missed.
I’d like to see more scientific study of the enneagram, but I know that many of the things we care about in personality psychology are hard to measure or study empirically. That doesn’t mean anything goes. You don’t get to say, this stuff is hard to study scientifically, therefore my theory about it is true. Any personality theory needs to be based in the reality of what people are like, even if quantitative methods can’t tell us everything. The advantage of quantitative methods over something like the enneagram narrative tradition is that you can get a larger and broader sample, and so you can find out whether the theory applies to a broad population, and not just to that group of people, probably not representative of the general population, who are interested enough in personality psychology that they will study these theories and spend time describing themselves. The advantage of the sorts of qualitative methods used in enneagram circles is that they tell us about what it’s like to be a certain type of person, and can more easily get at underlying motives and attentional stances. There’s a tension between providing rich personality portraits that tell us what people are like in human terms, and making claims that can be justified scientifically, and different theories fall on different parts of that spectrum. It would be better to have a theory that can do both well, and MBTI is probably most balanced in that respect, though not perfect.
All the personality theories I know about have flaws, even serious flaws, but each has interesting insights to offer.