Antonyms for the phrase "splitting down the middle" include words and phrases such as "united," "together," "whole," "intact," "unbroken," "unscathed," and "undivided." These words imply a state of cohesion, rather than separation or division. Antonyms can be useful in helping to convey a particular message, or to add variety and nuance to one's language, writing, or speaking. In many cases, antonyms can be employed to create contrast, emphasizing the differences between two opposing ideas. Choosing the right antonyms can help to convey a particular feeling or mood, and can make communication more interesting, engaging, and effective.