He was the only one who really believed in the Raggedy Doctor. He didn't believe in all the parts, he highly doubted that a magic blue box flew into her yard, but it was entirely possible that a strange man found a way into her yard and fixed her wall while her aunt was away. A very strange man, and a very bad decision on Amelia's part to let the dolt in, in his opinion. But, the past is done.
Well, he didn't truly believe until one day, when he received a call from Amy with the words, "Look outside."