The most fundamental aspect of Piaget's theory is the belief that intelligence is a process, not something that a child has, but something that a child does. Piaget's child does not possess knowledge, but understands the world by acting or operating in it. For example, Piaget would describe an infant's knowledge of a ball in terms of what he or she performs with it – pushing, throwing or mouthing it. These actions represent the cognitive structures of infancy and are called 'schemes'.