After spending many years exploring the Enneagram personality types, I've found that understanding and applying the types to one's life can be summed up in five parts. I've reorganized Dave's Enneagram website to provide web links and posts for exploring each part.
It's unfortunate that the enneatype writers have seemingly limited themselves to the concepts of aggressive, compliant and detached types within Karen Horney's work. Opportunities for applying other insightful aspects of her work to the enneatypes are missed. In discussing the idealized image in her book Our Inner Conflicts, she offers what can be seen as an interesting comparison between enneatypes 7, 4 and 1.
For most of us, our initial understanding of the nine Enneagram types comes from reading or listening to descriptions of the nine types. Although this gives us a clue as to what to look for, it's not until we hear the types describe their actual experience in their own words that we truly begin to know the types.
Typing yourself and others using the Enneagram types is a natural part of learning about and using the types. However, a lot of difficulties can arise when typing both yourself and others.
It may be true that most, if not all, type 4's have been depressed at sometime in their life. That may also be true of many Enneagram types. With type 4, depression, sadness or melancholy can arise as a byproduct of other processes or triggers.
What is objectionable, what is dangerous about extremists, is not that they are extreme, but that they are intolerant. The evil is not what they say about their cause, but what they say about their opponents.