Play in moving has evolved to use a muscular body with many parts, to invent projects that sustain vitality of the Self, and to animate a community. Young animals play to experiment with how to move joyfully when they try to master new skills in engagement with the world. The 'self-organising' systems of the embryogenic Intrinsic Motive Formation in brainstem and limbic cortex are of key importance in regulation of post-natal cognitive growth. They create the infant's curiosity, and all they control and express sympathetic and mimetic awareness of attendant persons and their human responses. Mastery of the moment with innate 'human sense' is created imaginatively through time and space in dreams and memories that extend modes of consciousness in conventions of activity, building what Margaret Donaldson calls 'common sense'. Like school education, the medical professions of paediatrics, psychiatry and psychotherapy have also had to overcome a neglect of the creative virtues of infant play.