The term “to split the baby” is an idiomatic expression for what seems like an unreasonable decision but is actually a ploy to flush out the truth. It is a psychological game: based on people’s reactions to his announcement, the decision-maker will be able to gather the right information. It is particularly effective when the existing data is confusing or even outright conflicting.
The idiom is rooted in the Biblical story of Solomon, found in the Old Testament in verses Kings 3:5-14. King Solomon, regarded as the wisest man in all of Israel, was approached by two women.
The women both insisted that they were the mother of the same child. One of them was obviously lying—as the story goes, she had accidentally smothered her baby in her sleep, and upon waking, had switched him with the baby of another woman living in the same house. That mother recognized that the child was not hers, and tried to get her own baby back. However, it was now a case of one word against the other. Who was telling the truth?
Solomon hears exactly the same story from the women, which makes traditional interrogation useless—it is a matter of finding out who is telling the truth. He announces that he will just “split the baby.” He will take a sword and slice the poor child in half, so that the mother can each have their own share.
Naturally this would kill the child instantly. However, Solomon looks at the reactions of the women to the story. One of them likes the solution; she has no attachment to the child and, having lost her own baby, finds jealous comfort in knowing the other woman will, too. The other immediately cringes and cries out, begging the king to spare the child even if it means giving him up. Clearly, she is the real mother.