"Truth" is dreams that don't come true, and nobody printing your name in the newspaper until you're dead. Big Daddy
Yes, the truth can be unpleasant, so the Pollitt family has chosen to live with lies - "mendacity", as Brick calls it. They're lying about everything: love, greed, death, guilt, parenthood, ambition, nostalgia, masculinity, and more. Then the facade comes crashing down all in one night, and we all get to witness the emotional carnage that ensues. There are so many fascinating sub-texts in Williams' story, not least of which is the irony of Maggie so desperately wanting the wealth and luxury that the Pollitts possess, contrasted with the utter emptiness and unhappiness of that same family, who have spent their lives with "things" but never love. Liz Taylor and Burl Ives are masterful here.