The body and the Soul

The Gestalt theorists, Koehler and Koffka, had shown that the atomic units of perception and learning, namely, ‘sense data’ and ‘the reflex arc,’ are not elementary but derived and a structure is not reducible to the interaction of atomic units. According to Merleau-Ponty, the Gestalists had misunderstood the ultimate implications of their own work, because they believed that the notion of structure can be thought within the naturalist ontology that subtended the thought of the atomists whom they had criticized.

The Gestalt theorists believed that structures existed in nature and that they do not cause atomic responses but rather structured responses. According to this view, behavior is still defined as a product of causality, but it is now a structural causality in which the structure remains a thing-like being. "The integration of matter, life and mind is obtained by this reduction to a common denominator of physical form".

Merleau-Ponty argues that the Gestalt exists for a perceiving subject; it is not a part of the world as it is in itself. The stimulus does not unilaterally affect the organism in virtue of its absolute physical and chemical properties; it becomes a stimulus only insofar as the organism constitutes for itself a vital milieu which it projects around itself. The mouse in The Metropolitan Museum of Art is affected by the crumbs of cookies on the floor, but not by the Velázquez painting on the wall. In the milieu that the mouse constitutes, the crumb is desirable and the painting does not exist.

In both the Phenomenology of Perception and The Visible and the Invisible, he elaborates a conception of the relationship between the body and the soul that both retains and transforms the conception presented in The Structure of Behavior. Against Descartes, he claims that this relation is not a relationship between two substances which would in some way connect with one another. On the contray, the three structures are integrated, one into the other, in such a way that it reminds the reader of Hegel's notion of sublation (Aufhebung) whereby the lower is both cancelled, as independent, and also retained.

When this synthesis is accomplished, the autonomy of the lower is annulled; however, the synthesis can become undone, in which case the autonomy of the lower structure re-emerges. When this synthesis is effected, the lower structure does not exist as such. "The appearance of reason and mind does not leave intact a sphere of self-enclosed instincts". Merleau-Ponty insists that when speaking of the physical, the vital and the human structures, one should not conceive of them as acting on one another in a causal manner. Bernard Flynn 2004 Stanford Encyclopedia of Philosophy