From the preface:
On the point that the [Salvation] Army ought not to take such money, its justification is obvious. It must take the money because it cannot exist without money, and there is no other money to be had. Practically all the spare money in the country consists of a mass of rent, interest, and profit, every penny of which is bound up with crime, drink, prostitution, disease, and all the evil fruits of poverty, as inextricably as with enterprise, wealth, commercial probity, and national prosperity. The notion that you can earmark certain coins as tainted is an unpractical individualist superstition. None the less the fact that all our money is tainted gives a very severe shock to earnest young souls when some dramatic instance of the taint first makes them conscious of it. When an enthusiastic young clergyman of the Established Church first realizes that the Ecclesiastical Commissioners receive the rents of sporting public houses, brothels, and sweating dens; or that the most generous contributor at his last charity sermon was an employer trading in female labor cheapened by prostitution as unscrupulously as a hotel keeper trades in waiters' labor cheapened by tips, or commissionaire's labor cheapened by pensions; or that the only patron who can afford to rebuild his church or his schools or give his boys' brigade a gymnasium or a library is the son-in-law of a Chicago meat King, that young clergyman has, like Barbara, a very bad quarter hour. But he cannot help himself by refusing to accept money from anybody except sweet old ladies with independent incomes and gentle and lovely ways of life. He has only to follow up the income of the sweet ladies to its industrial source, and there he will find Mrs Warren's profession and the poisonous canned meat and all the rest of it. His own stipend has the same root. He must either share the world's guilt or go to another planet. He must save the world's honor if he is to save his own. This is what all the Churches find just as the Salvation Army and Barbara find it in the play. Her discovery that she is her father's accomplice; that the Salvation Army is the accomplice of the distiller and the dynamite maker; that they can no more escape one another than they can escape the air they breathe; that there is no salvation for them through personal righteousness, but only through the redemption of the whole nation from its vicious, lazy, competitive anarchy: this discovery has been made by everyone except the Pharisees and (apparently) the professional playgoers, who still wear their Tom Hood shirts and underpay their washerwomen without the slightest misgiving as to the elevation of their private characters, the purity of their private atmospheres, and their right to repudiate as foreign to themselves the coarse depravity of the garret and the slum. Not that they mean any harm: they only desire to be, in their little private way, what they call gentlemen. They do not understand Barbara's lesson because they have not, like her, learnt it by taking their part in the larger life of the nation.