Abstract: Three experiments investigating children's understanding of inference as a source of knowledge and beliefs were used to determine whether children use a theory in understanding the mind. A child watched while a sweet was placed in a box whereas a doll was merely given a message about which sweet had been transferred. Children were asked to judge whether the doll knew the colour of the sweet in the box and what colour the do6 would think the sweet was. The main finding was that children tended to say the doll would hold a false belief about the colour of the sweet whenever the doll had not looked in the box. This result is easily reconciled with the theory view as a drive for coherence within the different aspects (knowledge and belier predictions) of the child's theory of mind. The result is contrary to the simulation view because children were generally good at‘inputting’or taking account of the relevant information (i.e. the doll's knowledge of the sweets’colours and the message to the doll), because children assessed their own beliefs quite differently from the doll's beliefs, and because contrary to the default assumptions set out by Harris (1991) children found it easier to assign a false belief to the doll than to assign a true belief.