I replied:
When we learn that London, instead of using its police for the running in of burglars and "drunks," is using them to lead an attack on Birmingham for the purpose of capturing that city as part of a policy of "municipal expansion," or "Civic Imperialism," or "Pan-Londonism," or what not; or is using its force to repel an attack by the Birmingham police acting as the result of a similar policy on the part of the Birmingham patriots—when that happens you can safely approximate a police force to a European army. But until it does, it is quite evident that the two—the army and the police force—have in reality diametrically opposed rôles. The police exist as an instrument of social co-operation; the armies as the natural outcome of the quaint illusion that though one city could never enrich itself by "capturing" or "subjugating" another, in some unexplained way one country can enrich itself by capturing or subjugating another.
In the existing condition of things in England this illustration covers the whole case; the citizens of London would have no imaginable interest in "conquering" Birmingham, or vice versa. But suppose there arose in the cities of the North such a condition of disorder that London could not carry on its ordinary work and trade; then London, if it had the power, would have an interest in sending its police into Birmingham, presuming that this could be done. The citizens of London would have a tangible interest in the maintenance of order in the North—they would be the richer for it.
Order was just as well maintained in