Michael Lewis thesis consists in completely dissociating intentionality and consciousness. Behaviors are intentional from the beginning of the sensorimotor stage whereas reflexive consciousness does not until the end of this stage, that is, around 18 months. He thus radically opposes Piaget's thesis according to which consciousness and intentionality are in close solidarity and progressively emerge in the course of the sensorimotor stage and give rise to human intelligence (psychic or mental activities). Lewis describes the development of intentionality in the sensorimotor stage in five levels closely related to emotional development. The major target aimed at by Lewis in his articles is Piaget. Now to start with, I have to declare my disagreement with his interpretation of Piaget. Therefore, I am bound to make explicit my own interpretation of Piaget for general as well as for specific issues raised by the article, and to initiate a first confrontation between Lewis and Piaget. Finally, I present my own critical position which consists in considering consciousness as a necessary transitional phenomenon for cognitive development and more precisely for redefining behavior determinants.