A drug addict entered a pawnshop with a starter pistol that could not fire real bullets, intending to rob it so he could buy drugs. However, once inside the pawnshop, the addict was too afraid to do anything and turned to leave. He bumped into another customer who was coming in as he was going out, and the pistol fell from his coat pocket. The shopkeeper saw it and realized what the addict had intended. She chased after him and flagged down a patrol car, and he was arrested a block away. The addict is charged with burglary, which is defined in this jurisdiction as "breaking and entering of any building for the purpose of committing a felony." His best defense would be which of the following?