I have been pondering correlations between the enneagram and MBTI that are very popular in personality typing circles. I wonder how valid these correlations are.
My main argument is that I have a hard time seeing how a system like the MBTI, which is about "cognitive functions" (brain) and the enneagram, a much more "existential" viewpoint (experience), can be associated with any kind of validity. On a theoretical level, the postulates of either have very little to do with one another. As such, the only valid association made between the two is simple observation of the frequency of certain types of one system belonging to types in the other.
The prime example I have for this is the fact that INTPs and ennegram 5s are often seen as being near equivalents. However, I fail to see how INTPs who are suppose to mainly think rationally, and e5's, who have learned to retreat, observe and gather information in order to deal with experience are part and parcel. I would argue that any intuitive, sensor, thinker or feeler that has learned to deal with life in this fashion could be a 5.
Or, how about an ISTP (artisan), who might be brutally honest about their feelings and has a need to express their individuality through their creativity, like a 4, because, say, they were a middle child and had a hard time being seen.
I believe that trying to associate the two systems is a disservice to those who wish to use them for self-understanding because the archetypes of the one are often erroneously transferred to the other.
PS. I can already poke holes in my argument. However, I'd like to hear what others would have to say about this. I am aware of my own personal bias since I type myself as an INFJ (NiTiFeSe) 5w4 sx/so. Any insights into this would be highly appreciated.