Common factors is outcome based research. Of course people can't be reduced to numbers, but studies have to quantify things to be published. Here is one excerpt, just from the internet, about the numbers. I've read more articles about it though.

In 1992, Michael J. Lambert summarized psychotherapy outcome research and grouped the factors of successful therapy into four areas, ordered by hypothesized percent of change in clients as a function of therapeutic factors: first, extratherapeutic change (40%), those factors that are qualities of the client or qualities of his or her environment and that aid in recovery regardless of his or her participation in therapy; second, common factors (30%) that are found in a variety of therapy approaches, such as empathy and the therapeutic relationship; third, expectancy (15%), the portion of improvement that results from the client's expectation of help or belief in the rationale or effectiveness of therapy; fourth, techniques (15%), those factors unique to specific therapies and tailored to treatment of specific problems.

I do realize that this is not the main focus of the thread and have tried to suggest so, to take it up more privately.

If we had healthy attachment, we would probably not be in therapy with that focus. T's don't have healthy attachment either; I never said they did. What I said is attachment is proven, part of all types of therapy, can't be ignored.

I already said that there is an earned secure attachment that results from the relationship with the T. The T doesn't have to have a healthy attachment to do the work. In fact, at least in what I've seen and done, Ts tend to bond with clients who match their own attachment styles.

Mine is fearful avoidant as I am. We both admit that openly, work with it, and have at least most times earned secure. But attachment is not the same across the board. You could have any number of attachment styles with different people in your life and at different times.

While there are some universals, such as common factors and attachment, there are not absolutes in anything. Things depend on the situation, the people involved, the time, the history, and on and on and on....