 In support of the second position, Simmons (2003) constructs an argument based on the three grades of sensory response defined in Sixth Replies (CSM 2.294–96; AT 7.437–39) and physiological and psychological accounts,in Optics and Treatise on Man, of the operations that form experience in early childhood. In brief: the first grade of sensory involvement starts with impingement of particles on the organs of sense and includes all their physiological effects; the second grade comprises the immediate effects produced in the mind as a result of its union with a body provided with sensory organs; the third grade, which is the first to involve intellect, comprises all the “judgments about things outside us we are accustomed to making in childhood” (CSM 2.295; AT 7.437). Simmons argues that the early scientific works ascribe two sorts of judgments to intellect—those that falsely project resemblance and those that construct the appearances of sensible things. She finds that the latter are associative cognitive acts that connect sensations of qualities with images drawn from memory (Simmons 2003: 554; on images and the intellect, see Letter to Mersenne, July 1641, CSM 3.186; AT 3.395). The model of clear and distinct perception promoted in Descartes’ later philosophical works hardly fits the construction of images and ill-considered judgments that engage the intellect of a young child (on the diversity of intellectual operations, see Simmons (2003: 565–75,  77–8).[4]  The upshot is that sense perception of the world features PQs and SQs and its purpose is practical rather than scientific (CSM 2.57–8; AT 7.83; CSM 1.223–4; AT 8.41–42.) Once we attain clear and distinct a priori perception of the essence and properties of bodies, we are unable to conceive how a body could resemble a sensory presentation of color, etc.