In an earlier publication, groups described by le Bon, Freud, and Eric Hoffer were interpreted as cargo-groups. This paper is restricted mainly to Bion, and is theoretical. Here Bion's therapeutic group, obeying his laws of dependence, fight/flight, and pairing, is interpreted as a maturation-group. Such a group is seen against the goal attributed to Bion of becoming a work-group. Other groups are reducible to these three types. Types in practice are mixed not 'pure'.

The aims of the paper are these: First, to contribute to the problem of why people have to belong to groups. Second, to characterize the three types of groups, and to explore the dynamics of how a group progresses to, or regresses from, one type of group to another. Third, to provide a structure permitting of emergent properties. This question is unresolved in the natural sciences; it is therefore likely to be a difficult question in the social sciences. It seems to be that Bion's study of groups provides a beautiful example of emergent group-properties.