In his paperLes e´piste´mologies constructivistes: Un nouveau commencement(Sciences de la Socie´te´, n°40, 1997), Jean-Louis Le Moigne poses the question:“Le re⁁ve d’une connaissance autore´fe´rentielle se fondant sur elle-me⁁me, est sans doute fascinant &ellip; Mais est-il scientifiquement raisonnable?”. Building on the work of Jean Piaget, I shall try to show through a developmental analysis of elementary, scientifically relevant concepts, such as ‘change’, ‘object permanence’, ‘space’, and ‘time’, that the notion of the thinking subject’s construction of knowledge constitutes a more reasonable foundation for science than the traditional belief in the representation of objective reality. ©1999 American Institute of Physics.