Misidentifying Sevens and Nines
Sevens and Nines might seem difficult to confuse since average Sevens are the hyperactive extroverts of the Enneagram, while average Nines are obviously passive and complacent, and live at a much lower energy level than Sevens.
The main reason they can sometimes be confused is that both types can be extremely busy and both are usually rather ebullient and happy. Furthermore, the defense mechanisms of both types are similar: both have repressed their inner worlds—Nines to maintain their identification with an idealized other, Sevens to avoid cutting themselves off from sources of external stimulation.
The points of similarity are reflected in their psychic structures–the fact that both are sensation types in the Jungian model, Sevens corresponding to the extroverted and Nines to the introverted sensation type (PT, 193 and 250). While it is clear from even a superficial acquaintance with Sevens that they are highly extroverted and orient themselves to the world via sensation, what is unclear is that Nines are introverted. What is even more unclear is the nature of the sensation that they introvert on. This is why the inner world of Nines is so obscure and difficult to describe (and why others have not understood this type's proper correlation to the Jungian category).
A deeper understanding of the Nine's psyche comes from realizing that the Nine orients itself to the world by introverting on the "sensation" of possessing union with another–by introjecting another, and then idealizing that introjection. To put this in simpler terms, their sense of self comes from the emotion they feel when they sense their identification with another person, much as a pregnant woman introverts with thoughts of love for her unborn child. By talking to the child in her womb, she gains a sense of herself as a mother. In a similar way, Nines commune with their inner sensations (identifications), maintaining their sense of self by living through an identification with another person. Hence they correspond to the Jungian introverted sensation type.
This introversion accounts for the inner life of Nines, which is largely out of view, protected in the inner sanctum of their psyches so that it cannot be easily disturbed or changed. It is in their dealings with the outside world that Nines can resemble Sevens.
Average Sevens are hyperactive, busy with too many things superficially. They dabble around to amuse themselves and to stave off boredom and anxiety. Similarly, Nines are highly intolerant of anxiety, and they stay busy to avoid it, using errands and hobbies to occupy their minds in undemanding, non-threatening ways. They want to avoid conflict or over excitement; by contrast, Sevens love excitement. Sevens become demanding and excessive and crassly materialistic as they deteriorate, while Nines become more passive, indifferent, and unresponsive as they become more unhealthy. Sevens want to be stimulated, whereas Nines want to avoid anything that would overly stimulate, much less upset, them. The essential difference is that average Nines do not want to be emotionally involved in their activities (since these can threaten their identifications), whereas Sevens want to have an increasingly high emotional charge from their activities (since they have few subjective identifications).
Furthermore, Nines do not seek the same kind of happiness that Sevens do (euphoria and elation). Instead, they wish to maintain a state of placid contentment, of being neither too excited nor in discomfort. Indeed, if they could, they would be completely free of excessive stimulation of any kind. The Nine's desire to avoid becoming deeply involved with anything lest it arouse too high a response is the polar opposite of what we find in the average Seven. As we have seen, like all opposites, these two types can nevertheless be alike in many ways. Consider the differences between John F. Kennedy (a Seven) and Ronald Reagan (a Nine) or between Bette Midler (a Seven) and Ingrid Bergman (a Nine) for further insight into these two types.