Article one notes in passing that process thought presses immanence. Process theology's specific technical account of how transcendence and immanence are held together, rather than merely which one is emphasised, is detailed enough to deserve its own treatment.
Alfred North Whitehead's metaphysics, developed from the 1920s, gives God two natures rather than one undivided simplicity. The primordial nature is God's fixed, eternal grasp of every possibility, unchanging and, in that sense, transcendent of any particular state of the world. The consequent nature is God's ongoing, changing experience of the actual world as it unfolds, affected and enriched by every event within it, immanence taken about as far as a coherent theology can take it: not merely God acting within the world but God being changed by it.
Charles Hartshorne developed the position into an explicit panentheism, arguing that the world exists within God as a later development of God's own being rather than as something merely accompanied by God, while insisting God still exceeds the world and is not exhausted by it, precisely the distinction article one draws between panentheism and simple pantheism. The classical theism article one describes rejects this framework at its root, since divine simplicity and immutability deny that God has two natures, or any parts, or that God's being could be really altered by anything external; process theologians reply that an unchanging God moved by nothing external is not obviously more biblical, and may be less so, than one transcendent in one respect and immanent enough to be changed in another.