Why is thought crime in which all others is contained ?

"The thought police would get him just the same. He had committed—would have committed, even if he had never set pen to paper—the essential crime that contained all others in itself. Thoughtcrime, they called it. Thoughtcrime was not a thing that could be concealed forever. You might dodge successfully for a while, even for years, but sooner or later they were bound to get you."

Because the crime exists within human mind, all crimes are rolled into one..... out thoughts.