First we must conceive of the enneagram as composed of nine 'zones', one zone associated with each enneagram point. In each zone gathers a 'family' of MBTI types that 'resemble' each other, although there is no one obvious feature which all members of the family have in common.
Furthermore, the family in each zone clusters around an MBTI pair that can be considered that zone's 'prototypes'. This protypical pair manifests a characteristic 'issue' (associated with their common inferior function) which all other family members, although they may have different fourth functions, also share in varying degrees.
For instance, associated with zone 8, as 'prototypical', is the 'extraverted thinking' pair (ESTJ, ENTJ). Both types have 'thinking' (T) as the dominant function. They are the only two 'extraverted thinking' types amongst the 16. But it is not dominant extraverted 'thinking' that they share with the other (non-prototypical) members of the zone 8 family, but issues associated with underdeveloped feeling . For the ESTJ and ENTJ are also the only two types that share introverted feeling as their inferior function. This can be seen by looking at their respective 'preference-orders': ESTJ = E\T-S-N-F, and ENTJ = E\T-N-S-F.
Now, some ESTPs and ENTPs may also test as 8s, although they do not have feeling as their fourth function. Nevertheless, we hypothesize, feeling will be underdeveloped in these particular individuals and it is this (and related issues) that they share with the others in zone 8 [more about this below].
The following chart correlates an 'inferior function' with each zone and specifies the pair that is the 'prototype' for each zone. [We will use the following 'shorthand' convention: the formula 'E(N/S)TJ' will substitute for 'ENTJ and ESTJ'.]
Zone Issue Prototypical
MBTI Pair The Preference Orders
for the Members of
the Prototypical Pair
8 Inferior introverted feeling E(N/S)TJ T-N-S-F & T-S-N-F
2 Inferior introverted thinking E(N/S)FJ F-N-S-T & F-S-N-T
3 Inferior introverted intuition ES(T/F)P S-T-F-N & S-F-T-N
7 Inferior introverted sensing EN(T/F)P N-T-F-S & N-F-T-S
5 Inferior extraverted feeling I(N/S)TP T-N-S-F & T-S-N-F
9 Inferior extraverted thinking I(N/S)FP F-N-S-T & F-S-N-T
6 Inferior extraverted intuition IS(T/F)J S-T-F-N & S-F-T-N
4 Inferior extraverted sensing IN(T/F)J N-T-F-S & N-F-T-S
Let us summarize what we have said so far.
There are nine 'zones', one zone associated with each enneagram point
In each zone gathers a 'family' of MBTI types
Prototypical of each zone (and each family) is a pair of MBTI types (specified above)
Each family, however, is not limited to the prototypical pair, but is comprised also of individuals of other types who share issues related to the inferior function of the prototypical pair
From the above chart it is easy to see that each zone will also have a special relationship with one other zone, with which it shares an inferior function. For instance, 8 and 5 both have inferior feeling (although they also differ, insofar as zone 8 has inferior introverted feeling, and zone 5 has inferior extraverted feeling). Also, 2 and 9 have inferior thinking; 3 and 6 have inferior intuition; and 7 and 4 have inferior sensing. When we drew a circle with the nine points on it and connected these complementary pairs, we were surprised to get the following symmetrical diagram: