In many of his plays, Shaw writes a preface for the reader which, in some cases, has very little to do with the play itself, but, in some cases, as with Major Barbara, it comments directly on the ideas found in the play. And as with this play, the prefaces are often rather lengthy and are divided into sections.
In the first section of this preface, entitled "First Aid to Critics," Shaw attacks one of his favorite groups of adversaries — those critics who sought to prove that he had no originality in his ideas and, furthermore, that his ideas were thinly disguised imitations of foreign philosophies, and those who said that Shaw was only "echoing Schopenhauer, Nietzsche, Ibsen." Instead, Shaw maintains in the Preface that he is influenced much more by writers native to the British Isles than by foreign writers, and he cites such authors as Charles Lever and such groups as the Fabian Socialists. Furthermore, the themes used in this play are themes that he has already used: (1) the conflict between reality and romantic posturing; (2) the presentation of a woman (Major Barbara) as an independent person rather than a toy (or plaything) of men, as was seen in Shaw's Man and Superman; as was also (3) the idea of the superman (Undershaft and Cusins) as the savior of society.
Second, in "The Gospel of St. Andrew Undershaft," Shaw reinforces Undershaft's position that poverty is the greatest of all evils and the worst of all crimes. Here, Shaw is using evil and crime in a different sense from that of the average reader's understanding of the words. Shaw would defend a theft which a poor working man might commit — that is, if he were likely to have "to see his children starve whilst idle people over-feed pet dogs." This type of unfair distribution of wealth leads, naturally, according to Shaw, to various types of justifiable crimes. Shaw wants not only "legal minimum wages" and "old age pensions," but he also advocates "universal pensions for life." That is, Shaw believes in the redistribution of wealth so that no person need go hungry or be in want. If the person receives money from the government, he should also be provided some sort of work so as to earn that money. He ultimately suggests that all poverty should be illegal. In a perfect society, money is the most important thing; "it represents health, strength, honor, generosity, and beauty." When poverty is eradicated, the morals of a nation will naturally be taken care of.
In the third section, "The Salvation Army," Shaw seems to be having fun needling the critics who do not know how to respond properly to his use of the Salvation Army. Whereas some critics have accused him of attacking the Salvation Army, Shaw maintains that even the Army itself understands perfectly well the necessity of taking "tainted" money in order to continue its operations. In fact, it rings somewhat false that Major Barbara ever refused the money in the first place.
In "Barbara's Return to the Colors," Shaw maintains that there is something basically appealing about substituting a drum for the organ, as did the Salvationists when they went about marching through the streets instead of merely sitting and praying. Ultimately, Barbara must learn that bribing people to salvation through "bread and treacle" is not as noble as is converting people to their own accord. At least it is to be hoped that Barbara's knowledge "will clearly lead to something more hopeful than distributing bread and treacle at the expense of Bodger."
In the next section, "The Weaknesses of the Salvation Army," Shaw acknowledges that the Army, at present, is building a worthy and efficient "business organization," but he feels compelled to point out some of its weaknesses. Basically, he says, there is still "too much otherworldliness about the Army." That is, the Army emphasizes that salvation exists in the next world whereas Shaw wants to correct poverty and injustice in this world, immediately. The Army encourages the "nasty lying habit called confession." Shaw thoroughly dislikes any system that allows confession as atonement for sin (crime) because confession will allow the offender to feel free to commit the same offense again. Finally, the Army, instead of coddling the poor, should be encouraging them to stand up and demand their rights.
In "Christianity and Anarchism," Shaw refers to a recent international event (a royal wedding followed by a bullfight and an explosion) in which demands were made that cruel punishment be meted out to the offending rebels. For Shaw, this is not Christianity, but "Crosstianity"; it is pure vengeance disguised under the cloak of Christianity. Instead, for the church to be true to itself, it should not conspire with the state to keep "the poor in their places" but, instead, should emphasize a true sense of equality and brotherhood among people.
In "Sane Conclusions," Shaw reemphasizes some of his points. First, every able-bodied person must be expected and allowed to work and to earn money commensurate with his efforts. The wealth of the nation should be in proportion to the efforts of the workers; and second, all harsh, unusual, and cruel punishments should be abolished. Such punishments waste manpower that could be put to better uses. Next, Shaw maintains that there should be talk of atonement: "A man's deeds are irrevocable," and he must be held responsible for them. A man's life is to be measured in relationship to his usefulness to society. Finally, Shaw urges all institutions, especially the church and the Salvation Army, to become intellectually honest — to recognize true "mischief" for what it is and not to offer atonement and not allow an offender to be redeemed by mere expressions of repentance and confession.