This article explains how it is possible to arrive at the paradoxical conclusion that an increased reliance on private actors (in the guise of private military companies) could consolidate public peace and security in the weakest African states. It argues that this conclusion can only be reached if the dynamics of the market for force are neglected. The basic claim is that the market as a whole has effects that cannot be captured by focussing on single cases. The article analyses these effects, departing from the empirical functioning of supply, demand and externalities in the market for force in order to spell out the implications for public security. More specifically, the article shows that supply in the market for force tends to self-perpetuate, as PMCs turn out a new caste of security experts striving to fashion security understandings to defend and conquer market shares. The process leads to an expansion of the numbers and kinds of threats the firms provide protection against. Moreover, demand does not penalize firms that service 'illegitimate' clients in general. Consequently, the number of actors who can wield control over the use force is limited mainly by their ability to pay. Finally, an externality of the market is to weaken existing security institutions by draining resources and worsening the security coverage. This gives further reasons to contest the legitimacy of existing security orders. In other words, the development of a market for force increases the availability and perceived need for military services, the number of actors who have access to them and the reasons to contest existing security orders. This hardly augurs well for public security.