Books: Two Against One

On coalitions in triads.

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“A triad is a social system containing three related members in a persistent situation” writes sociologist Theodore Caplow. “The most significant property of the triad is its tendency to divide into a coalition of two members against the third” (p.1).

So begins Caplow’s 1968 Two Against One: Coalitions in the Triad.  The book presents a general theory that aims to explain, for any given triad, which if any members will form a coalition against the third. The theory uses the rational choice paradigm, modelling social actors as rational agents seeking to maximize their gain. The main variable that explains coalitions is the distribution of power: “The appearance of particular coalitions can be predicted with considerable accuracy if the relative power of the three members is known” (p.2).

Caplow starts with a hypothetical example: Imagine three smugglers alone on an island, deciding how to divvy up their loot.  Two of the smugglers are equal in strength. The third is stronger than each of the others, but weaker than the both of them joined together.  The most likely coalition would be between the two weaker smugglers.

The reason is that people choose allies based on the advantage of the partnership to themselves.  In our smuggler example, neither of the weaker parties would have a reason to form a coalition with the stronger one, because in such a coalition they’d still wind up being dominated by the strongest. They’d still be less likely to receive an equal share of whatever goods were being divided.

But in a coalition between the two weaker equals, neither has to worry about being dominated by the other — they’re evenly matched. And by joining together, both can avoid being dominated by the strongest. In this way they maximize their share of the loot. The rational and therefore most likely strategy is for the two equally weak parties to club together against the stronger third.

This example shows the basic logic with which Caplow predicts coalitions. It also points to an interesting property of coalitions: Sometimes strength can be a weakness, in that it keeps one from being a preferred coalition partner. The strongest party in the triad might well be the one who winds up getting dominated.