In Chapter 15, Dorothy seeks to understand the paradox of Oz's ability to appear in multiple fantastical forms if he is simply a regular man:
‘But, I don’t understand,’ said Dorothy, in bewilderment. ‘How was it that you appeared to me as a great Head?’
‘That was one of my tricks,’ answered Oz. ‘Step this way, please, and I will tell you all about it.’
He led the way to a small chamber in the rear of the Throne Room, and they all followed him. He pointed to one corner, in which lay the Great Head, made out of many thicknesses of paper, and with a carefully painted face.
Oz appeared to Dorothy as a giant head, and he appeared to each of her friends in a different form. When they go to see him as a group, he disguises himself as a disembodied voice. His ruse almost works, but Toto knocks over the screen he is hiding behind. The characters see that Oz is a small, unimpressive, wrinkly old man. The booming, disembodied voice was a stage trick. But Dorothy cannot entirely let go of her impression that he his magical and all-powerful. After all, how else would he have passed himself off to different characters as a giant head, a beautiful lady, a terrifying beast, and even a ball of fire? Dorothy and her friends are not all delusional. Logically, Dorothy concludes, there must be some way Oz got all of them to see him in a different form.
There is, in fact, an explanation for how Oz pulled off his many different appearances, but there is no magic involved. He shows Dorothy the paper head he suspended from the ceiling when he spoke to her, and he explains how he pulled on a wire to make it look like the head was speaking. He tells her that he is a ventriloquist, so he was able to make it sound as though his voice was emanating from the large paper mouth, as well. Then, he goes on to show the characters the other props he used to fool them.
The paradox demonstrates that Dorothy is no foolish child. There are real, logical reasons to believe that Oz is a wizard. And yet his explanation of the paradox demonstrates that Dorothy should not always trust her eyes. Appearances can be deceptive, and sometimes people are actively and craftily trying to deceive others. This moment serves as an important lesson for young readers: just because someone looks far more powerful and talented than you does not mean they actually are.
