The importance of childhood, in Spinoza's thought, is generally under-valued or poorly evaluated. The study of a theme that is, at first glance, marginal in an author often appears as a frivolous pastime, but it can be justified not only if this theme is the object of an original treatment, but if it plays a role in the general economy of the thought. These two prerequisites seem to be satisfied here. Spinoza's relationship to childhood is all the more remarkable insofar as it never solidifies into a position. One could even call it contradictory – as if there were a link with the situation in which reason is forced to face its other in the guise of the age that is reputed to be without reason. So too Spinoza begins by admitting that he doesn't really know what to think about childhood. His disparate remarks, by their problematic coherence, nevertheless open onto a horizon that is distinct from all other thinkers of the seventeenth century, Locke included. Upon reflection, it would have been surprising if that were not the case: how could one imagine that the state of inquiry in the Dutch golden age – what is childhood: a mutilated humanity or a world apart? the supreme humiliation or a happy madness? – how could this not have led this thinker who demystified the ideas of privation and metamorphosis to be philosophically overinvested in the first period of life? When at the end of the Ethics the whole of ethical progression or becoming-philosopher is identified with the becoming of the child that grows up, the entire Spinozist economy of images is at play, explicitly having in view an emancipated imagination, all the better freed of chimeras as it becomes ‘more distinct and vivid’ and the more it is ordered under the guidance of the mind. In order to confront the problem, Spinoza needed to make a strange but necessary detour through a figure that curiously has the air of a chimera: the infans adultus, adult-child or child-adult.