Both poems convey a parent's fears about the difficulties facing the child or young adult who has to grow up in this often frightening and uncertain world. In "If—," the speaker conveys hope as he describes for his son the virtues he perceives as necessary for successfully managing life. In the first stanza, these include trusting oneself, not repaying evil with evil, and behaving modestly: "don’t look too good, nor talk too wise."
In stanza 2, the father advises his son to balance dreaming and thinking with action and to keep a level head in both good fortune or disaster. He counsels him not to be crushed by adversity and other people's malice but to quietly rebuild when his work is broken. In stanza 3, the father advises his son to not care too much about money and to keep a stiff upper lip, not revealing his feelings no matter what befalls him. Finally, in the last stanza, the father tells his son to treat all people with the same courtesy, be they kings or commoners ("crowds") and to maintain an aloofness and self-integrity. These are the ingredients that make a "man," according the speaker—"if" the son can manage them.
In Louis MacNiece's "Prayer before Birth," the speaker projects his fears about the world onto his unborn child. This unborn babe asks for protection against a list of dangers that are not dissimilar (if not identical either) to those the speaker in "If—" tries to deflect. The unborn babe wants to be free of drugs, lies, and violence. He asks for closeness to the natural world and forgiveness for the sins he will commit just by being alive in a fallen world. Like the son in "If—," he would benefit if his father would "rehearse [him] / in the parts [he] must play and the cues [he] must take" when faced with adversity. Finally, in the last section, he asks for "strength" against those who would "freeze my humanity." He ends with saying he would rather be killed than be turned by life into a hard, inhuman person.
Both poems attempt to address what it means to live a meaningful, humane life in an evil world. Both assert it requires strength and a sense of decency to navigate the pain and adversity that inevitably face all people.