The term differentiation comes from biology. It is the scientific concept that most closely matches the processes Dr. Bowen was observing within families and between families. People vary across a broad continuum in their ability to function as emotionally separate individuals while being in good emotional contact with important others in their families and workplaces. This is a naturally existing continuum that develops over several generations. It is neither bad nor good; it just is.
At one end of the continuum are individuals who are the most underdeveloped as persons, the most relationship focused. They have the least self. They tend to live life in reaction to others rather than out of their own well-defined beliefs and principles. They have little tolerance for short-term discomfort and delayed gratification. Short-term urges tend to dictate their lives at the expense of longer-term goals and gains. They are very sensitive to what others think about them. Feeling and anxiety states tend to dominate their behavior and decision-making. This leads to swings between being overclose/positive and overdistant/ negative. Their behavior is often at the expense of someone: themselves, their loved ones, employers, friends. They tend to have the most life problems.
At the other end of the continuum are those who are most fully developed as persons, who have the most self. They have clearly thought out beliefs and principles. Their behavior matches these beliefs and principles most of the time. They function consistently as persons in all their roles and responsibilities in life unless under very high levels of stress. They can experience strong feeling and anxiety states without losing their capacity to think and act more objectively and in the long-term best interest of self and other. They are able to assume high levels of self-responsibility and leadership in family, workplace and society.