“No two individuals in the history of the human race have been born at the same instant, to the same parents, in to the same family and culture, with the same genetic endowment, educated in the same way, and the subject of precisely the same influences. What makes us unique is our unique history. But what makes us part of a personality type is the fact that we also share certain traits with other human beings. Although we are unique, we are not totally different. It would be an impossible world if everyone were literally completely unique, that is, if everyone were a totally dissimilar entity until himself or herself. Language, literature, the arts, commerce, communication – all of society and culture – would be impossible if people did not have a great many qualities in common.” (Riso & Hudson, 2000, p. 20-21)
Riso, D. R., & Hudson, R. (2000). Understanding the Enneagram: The practical guide to personality types (Rev. ed.). New York, NY: Houghton Mifflin.