Drawing on new evidence from the Dewey archive, this paper traces how John Dewey conceived his Hegelian-inspired theory of mind and how he tested it in the 1930s by collaborating with infant experimentalist Myrtle McGraw in her pioneering studies of the ontogeny of consciousness and judgment. Her studies challenged behaviourism and maturationism, which advanced environmental and genetic theories of human development, by showing that infants possess consciousness and the judgment needed to guide their own development. Dewey drew on Darwinian evolution and neuroscience to transform the Hegelian phenomenology of being and becoming into psychological terms that would elucidate the role of mind, consciousness and judgment in human experience. Dewey believed that consciousness arises under conditions of uncertainty demanding ingenuity, self-confidence and a sense of balance. McGraw demonstrated how infants cope with uncertainty and the physical challenges posed by gravity and the biological forces of growth, by exploiting the contingencies of order and variation afforded by their experience of motor development. McGraw demonstrated how consciousness emerges through reciprocal processes of neural and behavioural interaction which make possible the introduction of novel changes in ontogeny. This paper describes the extraordinary methods that McGraw devised, with Dewey's help, during the heyday of behaviourism and maturationism, to find a place for consciousness in human development. I contend that, while Dewey's theory of mind and McGraw's discoveries remain controversial and poorly understood, they are not merely of historical interest but approach the threshold of an integrated neurobiological and neurobehavioural understanding of consciousness.