ABSTRACTThis essay is about Jean Piaget’s late theory, but it is also an advance of my broader historiographical argument regarding the role of intellectual history in uncovering our science’s still-relevant “neglected invisibles” (introduced in Burman, 2015). It does this by building on recent scholarship in the History of Biology to show how Historians of Psychology can contribute to contemporary science without falling prey to “presentism” (i.e. the bias introduced into historical narratives as a result of the framing afforded by contemporary concerns). To wit: when the present itself has been biased by past disciplinary politics, then it is not “presentist” to show that this bias exists. Nor is it presentist to follow the consequences o...