unless

The Once-ler: And all that the Lorax left here in this mess was a small pile of rocks with one word. 
Boy: [reading it] "Unless?" 
The Once-ler: Yes. "Unless." 
Boy: What's an unless? 
The Once-ler: [sung] Just a far away word/just a far away thought... 
Boy: A thought about what? About something I ought? 
The Once-ler: [sung] Well... A thought about something that somebody ought/a thought about something... that somebody... ought. 
[spoken] 
The Once-ler: Unless someone like you cares a whole awful lot, nothing's going to get better. It's not.