Emergence is incoherent from physical to mental events One cannot speak of Whitehead's philosophy without referring to most primordial element if his philosophy. Without this primordial element, his metaphysics is incomplete if not totally empty.
Following is an excerpt which describes the necessity of any Creative Force in a complete metaphysics, which was why it is primordial Whitehead's process metaphysics.
http://people.bu.edu/wwildman/bce/whitehead.htm
Alfred North Whitehead (1861-1947)
The Necessity of God and the Divine Natures
"The system thus far described is incomplete in that it cannot adequately explain the foundations of the creative advance into novelty which characterizes the universe. As Hosinski points out, there are three questions which remain unresolved (see Hosinski, 156-163). The first relates to potentiality. If actual occasions merely prehend the objective forms of the past, the world would be a very dull place."
"The second as-of-yet unanswered question regards the origin of subjectivity. One can explain the steps involved in the development of a subjective aim in the process of concrescence, but one still needs to locate the origin of the initial subjective aim."
"The final question which remains unanswered is as to the order and value evident in creation. Whitehead asserts that there must be certain categorial conditions which undergird the unfolding of the creative process."
"The answer to these questions as to the origins of potential, the initial subjective aim, and order and value is God. God is the atemporal actual occasion which provides the world with its aims and with the eternal objects which guide creation. God must be an actual occasion, for according to the ontological principle, the reality of the initial aim, general potential and order and value must issue forth from an object of experience. God is not an afterthought to the system, but rather an integral part to its operation and description of both process and reality. God is the reason (and therefore the entity) which makes the existence of other actual entities possible. God "provides the limitation for which no reason can be given: for all reason flows from it. God is the ultimate limitation, and His existence is the ultimate irrationality" (SMW, 257). This is not to suggest that God is truly irrational, but God is the precondition for the existence of rationality."