Alice had started to believe that most things might be possible, suggesting a shift in her view of the world around her. This idea reflects her curiosity and open-mindedness as she explores the strange and magical world she has entered.
According to Lewis Carroll in Alice's Adventures in Wonderland, Alice's perspective is constantly evolving as she encounters bizarre and fantastical events. Her thoughts about impossibilities highlight her developing understanding that the boundaries of what is possible can often be questioned.