This is the first booklength account of how Maurice Merleau-Ponty used certain texts by Alfred North Whitehead to develop an ontology based on nature, and how he could have used other Whitehead texts that he did not know in order to complete his last ontology. This account is enriched by several of Merleau-Ponty's unpublished writings not previously available in English, by the first detailed treatment of certain works by F.W.J. Schelling in the course of showing how they exerted a substantial influence on both Merleau-Ponty and Whitehead, and by the first extensive discussion of Merleau-Ponty's interest in the Stoics's notion of the twofold logos--the logos endiathetos and the logos proforikos. This book provides a thorough exploration of the consonance between these two philosophers in their mutual desire to overcome various bifurcations of nature, and of nature from spirit, that continued to haunt philosophy and science since the 17th-century.