What structural conditions must any adequate ground of being satisfy? This paper argues that the grounding function imposes exactly three such conditions — generativity, non-coercion, and coherence — each independently necessary, and that no fourth condition is possible. The argument proceeds by identifying the irreducibly distinct aspects of what any ground must account for (the arising of genuinely other, determinate, intelligible beings), deriving one structural dimension from each, and demonstrating by a two-condition test that no fourth dimension can be added. The three-dimensional result is shown to be consistent with, and to underwrite, the binary diagnostic map employed in the eliminative argument of companion papers. The paper's contribution is to convert an assumed structural axiom into a formally derived result: the three-condition framework is not a definitional choice but a forced consequence of the minimal characterisation of grounding.