In Enneads 5.143, Plotinus reasons: “If the First is perfect, the most perfect of all, and the primal power, it must be the most powerful of all beings and the other powers must imitate it as far as they are able. . . . Fire warms, snow cools, and drugs act on something else in a way corresponding to their own nature—all imitating the First Principle as far as they are able by tending to everlastingness and generosity. How then could the most perfect, the first Good, remain in itself as if it grudged to give of itself, or was impotent, when it is the productive power of all things?”
It doesn’t take much to turn this into a gloss on Trinitarian theology: Plotinus’s argument implies either a First Principle that must diffuse itself generously toward the world, or a First who generously diffuses Himself in a Second equal to Him. On the first model, the First Principle is dependent on the world to which he/it diffuses himself. In the second, the first is the Father who gives Himself wholly to His Son by His Spirit.