Claim. Joy cannot arise from an individual alone — it requires an object partner in which one’s internal nature and external form are reflected, stimulating the self to feel its own qualities. This applies to humans and to God; it is why God needed substantial object partners (creation) to feel His original nature and experience the fullness of joy.
Elaboration. Per 3.2. Good Object Partners for the Joy of God: “joy is not produced by an individual alone. Joy arises when we have an object partner in which our internal nature and external form are reflected and developed. Our object partner helps us to feel our own internal nature and external form through the stimulation it gives. This object partner may be intangible or it may be substantial.”
The artist analogy makes the structure visible: “For example, an artist’s object partner may be an idea in his mind, or the finished painting or sculpture which substantiates that idea. When he visualizes his idea or beholds his work, he is stimulated to feel his own internal nature and external form reflected in it and feels joy and satisfaction. When his idea alone is the object partner, it is not as stimulating, nor is the joy that it brings as profound, as that from a finished work” (ibid).
The theological consequence: “God feels the fullness of joy when He is stimulated by His substantial object partners to feel His original internal nature and original external form through them” (ibid). DP commits to a God self-sufficient in existence but not self-sufficient in joy — God needed creation to experience the fullness of His own being. This grounds DP’s theology of divine emotion and divine suffering: when humans fall, God’s joy is genuinely diminished. Creation is constitutive of God’s full realization.