Semmelhack, Hazell, and Ende (2013) present seventeen years of quasi experimental studies that demonstrate the therapeutic effectiveness of Tavistock style groups with those diagnosed with severe mental illness. In these studies, significant improvements in anxiety, depression, coping, and group cohesion were found in members of Tavistock style groups. In addition, Semmelhack, Ende, Freeman, and Hazell (2015, pp. 187–211) describe in more detail the dynamics that took place in these groups. In this section, it is our aim to further explain the reasons why the Tavistock group can promote such growth. Such an explanation seems apposite because the Tavistock group is not intended to provide therapeutic benefit and groups in this tradition are usually regarded as not having especial therapeutic potency. Hill, for example (1965) ranks the “group/confrontive” intervention as eighth on a one to sixteen scale of therapeutic effectiveness. The above-cited studies by Semmelhack Hazell, and Ende (2013) call this rating into question. In this section we will attempt to show why the Tavistock style group has such effectiveness. We will do so by using Hill’s three vectors of therapeutic action (1965), namely: member centeredness, interpersonal threat, and therapist role taking in addition to positing several other dynamisms that could have therapeutic impact.