The promise rests on a single seed, not a scattered many, and the point turns on that oneness. Abraham is faith, and his seed is what faith produces: one unified power rather than a crowd of separate efforts. Scattered wishing divides and cancels itself. One clear conviction gathers a person and bears fruit.
That single seed is named the awakened imagination, the concentrated feeling of the wish already fulfilled. A man does not reach his good through many hopes pulling in different directions. He reaches it through one assumption held whole. The promise was always to the one, because only an undivided state carries the force to become fact. Everything a person receives grows from a seed he planted as a single, settled belief.