It may be impossible to define oneself without having other people for contrast. One's spouse may provide a consistent reflection of differences and similarities becoming as essential as a limb but for identity. So much so that the loss of a spouse, through death or separation, may be such an insuperable loss that one attempts suicide or reflexively creates a surrogate for the spouse. 1968's The Odd Couple shows two men in this predicament who bond through their mutual need for this other. It's a very funny film with great performances from Jack Lemmon and Walter Matthau, particularly Walter Matthau.
The film opens with Felix (Lemmon) attempting suicide while the looping theme song plays on the soundtrack, a lightly troubled tune which seems to both belittle and sympathise with Felix's dilemma. His wife has just announced she wants a separation so the devoted husband and father finds himself absolutely bereft. When he can't get the window open in the lofty hotel room he rents to throw himself out of, he hurts his back, so decides to wander the town until winding up back at the usual weekly poker game at Oscar's (Matthau) apartment.
One thing leads to another and the fastidious Felix ends up moving in with the sloppy Oscar. Oscar's apartment is huge with several bedrooms, a relic of his own failed marriage. He seems much better adjusted than Felix not only because he's had more time but there seems to be a flexibility permitted by Oscar's careless mode of life that is not allowed into Felix's tightly organised world. The battles the two have over the cleanliness of the apartment become like manifestations of their respective psychological issues--Oscar's fear of confronting the void in his life and Felix's obsession with confronting it.
At the same time, the conflict creates for each man a new complementary other in his roommate. Both accidentally refer to the other using the names of their ex-wives in a rather blatant symbol of this process coming to completion.
Jack Lemmon was great but I really loved Walter Matthau in this film. His delivery is odd and appropriate in such ingenious ways.