The motif and idea of who "belongs" and the idea of "belonging" are continually reinforced throughout The Hairy Ape. Yank equates "belonging" with power and importance and uses "belonging" as a way to reverse societal power structures. In Scene One, Yank claims that he "belongs" to the ship, as opposed to the passengers in first class who are merely "baggage." Yank also associates "belonging" with an individual's usefulness and functionality. The firemen "belong" because they make the ship run and are essential to its workings.
Yank is especially affected by Mildred because she presents a world and class which he cannot belong to. After their meeting, the play essentially follows Yank in his quest to find belonging, finally leading him to the monkey- house at the zoo.
For Yank, thought is the ultimate boundary. Whether pressing his fingers to his head or sitting in the position of Rodin's "The Thinker," he cannot muster enough thought to make sense of or come to peace with the world around him. Thought only becomes necessary for Yank after he encounters Mildred in the stokehole. Mildred and he class present a new threat that Yank cannot eliminate or get rid of by physical might. Yank is forced to think how he can defend himself. This transition is exemplified in the "tink" joke among the men. Before Mildred enters the stokehole Yank finds thinking ridiculous and unnecessary, he laughs when he tells the other men he is "trying to tink." However, after the encounter, Yank earnestly tells the men that he is trying to "tink." When they joke and correct him in a mocking chorus, "Think!," he is genuinely hurt.
Yank's inability to think not only reveals his regression to a lower animal form, but also renders him unable to adapt to or defend himself in the world beyond the ship.
Yank's idiosyncratic speech, characterized by chopped and mangled words eliminate the possibility of Yank's successes or acceptance in a world or class other than his own. His deformed language makes real communication impossible. Ann Massa in "Intention and Effect in The Hairy Ape" puts it quite beautifully, "Yank can only break the bounds of his vocabulary and his style in the same violent and ultimately frustrated way that he bends the bars of his cell he can't break the mould of the apparently flexible yet imprisoning medium that is language and that is life." Yank's speech defines his class and place in society—rigid, unchanging and binding.
The settings and environments of The Hairy Ape reveal larger social and cultural realities. Yank and the Firemen exist within the cramped and hot forecastle and stokehole, described as a formidable cage. In contrast, Mildred and her Aunt's environment, the Promenade Deck of the ship, is filled with fresh air and sun. The ocean that surrounds them is infinitely spacious and the general feeling of freedom abounds. The promenade deck is also symbolically situated above at the top of the ship, far above the stokehole. Both the stokehole and the promenade deck setting epitomize the lifestyles and characteristics of the ship's literal decks and subsequent upper and lower classes aboard.