Topic 1: Grouping

Grouping is one of the most fundamental aspects of thinking. Although it is not a reasoning activity, a solid grasp of grouping is very important for good reasoning and argument, since in complex arguments reasons ought to be properly grouped together.

The basic notion of a group is very simple and familiar:

A group is a collection of items which belong together in some way.

Grouping is just the activity of creating or specifying groups. It involves

- identifying a suitable grouping principle (see below),

- identifying the items which belong to the group thus defined, and

- presenting the items in a clear and orderly way.

Grouping Principle

A grouping principle is an explicit statement of the essence of the group, i.e., the sense or respect in which the items belong together. It is important to articulate the grouping principle as clearly and precisely as possible. Often groups are poorly formed because the grouping principle is confused or vague.

Coherent Groups

Here ‘coherent’ just means properly thought-out and presented. A coherent group should be:

1. Complete	No gaps, nothing missing; everything which belongs in the group should be present.
2. Internally Distinct	No overlaps; each item in the group should be genuinely distinct or separate from all the others.
3. Minimal	No outsiders; nothing should appear in the group which does not really belong.
4. Ordered	Items should be listed in the most natural or appropriate order.

Figure 2.1 Countries listed in order of GDP (IMF rankings)

MECE

Sometimes the acronym MECE is used as shorthand for a properly formed group. MECE stands for ‘Mutually Exclusive, Collectively Exhaustive’ and is just a fancy way of saying ‘no overlaps, no gaps.’

The problem with MECE, however, is that it does not conform to itself; MECE is not complete as a list of the properties of a properly formed group (i.e., its two principles are not ‘collectively exhaustive’).