Falsehoods and untruths
Mendacity is a recurring theme throughout the play. Brick uses the word to express his disgust with the "lies and liars" he sees around him, and with complicated rules of social conduct in Southern society and culture. Big Daddy states that Brick's disgust with mendacity is really disgust with himself for rejecting Skipper before his suicide. With the exception of Brick, the entire family lies to Big Daddy and Big Mama about his terminal cancer. Furthermore, Big Daddy lies to his wife, and Gooper and Mae exhibit avaricious motives in their attempt to secure Big Daddy's estate. In some cases, characters refuse to believe certain statements, leading them to believe they are lies. A recurring phrase is the line, "Wouldn't it be funny if that was true?", said by both Big Daddy and Brick after Big Mama and Maggie (respectively) claim their love. The characters' statements of feeling are no longer clear-cut truths or lies; instead, they become subject more to certainty or uncertainty. This phrase is the last line of the play as originally written by Williams and again in the 1974 version.
The ways in which humans deal with death are also at the focus of this play, as are the futility and nihilism some encounter when confronted with imminent mortality. Similar ideas are found in Dylan Thomas's "Do Not Go Gentle Into That Good Night", which Williams excerpted and added as an epigraph to his 1974 version. These lines are appropriate, as Thomas wrote the poem to his own dying father.
Additionally, in one of his many drafts, in a footnote on Big Daddy's action in the third act, Williams deems Cat on a Hot Tin Roof a "play which says only one affirmative thing about 'Man's Fate': that he has it still in his power not to squeal like a pig but to keep a tight mouth about it."