Let us return to the example of Mach’s square. Merleau-Ponty employs it to level a critique against Gestalt psychology, exposing residual commitments to realism: lingering assumptions of objectivity that persist despite its major theoretical advances. His aim is to underscore the insufficient analysis of the epistemological and ontological presuppositions underlying the psychology of form. In contrast to the Gestaltists’ reading of Mach’s square, which stresses the functioning of the visual field by highlighting the dissimilarity between the two figures, Merleau-Ponty observes that judgment, insofar as it involves asserting the equality or difference of the figures, presupposes retaining the first as a reference. We perceive the oblique figure as a square not because we immediately refer to the square as seen frontally, but “because the diamond-shaped appearance in an oblique presentation is immediately identical to the square appearance in a frontal presentation” (PP, 350). Yet these appearances are not immediately identical: we recognise them as such only subsequently, through a process of calculation or comparative reasoning applied to the figures. The two configurations are, in fact, immediately perceived as different: the oblique figure does not “remain a square” (PP, 350).