http://theenneagram.blogspot.com/200...-6s-vs-4s.html

It's about some integral similarities between 4's and 6's. It deals with the cognitive awareness [T] - intellectual, inner knowing; the emotional awareness [F] - emotional, sense of self; and the motivation [M] - acting, implementing. Essentially, it contrasts the dynamics of each of these facets within the 4 and 6 personalities.

6 Centers: [T] F⇒M
The 6 is cut off from their inner knowing, while consistently residing in their sense of self [F], which is based on feelings of fear, loyalty, rebellion, etc., due to the separation from internal guidance. In order to reconcile this, they act based on these feelings [M], substituting external things to compensate for the lack of inner knowing.

4 Centers: T⇒F M
The 4 naturally resides in their emotional sense of self [F], but their is a block on it (not knowing the "true" self), so they use their intellect [T] to fuel the process of idealizing and cultivating emotions [F] in an attempt to attain this. They are not cut off from their inner knowing [T]; in fact they are too in touch with it. Their desire to act on their sense of self or knowing [M] is generally disregarded, unless it facilitates their sense of self. They tend to simply react based on these things, which is typically unproductive.

What's interesting is, this type of diagram could probably be applied to all the other types. For example, the 7 is cut off from their feelings, and uses their thinking to fuel their motivations, so as to avoid feeling empty and give the illusion of security -- [F] T⇒M. And so on...