The article is an analysis of the logic of a posteriori modal proofs of the divine existence. A certain general principle of modal proofs is being identified: namely, the inference to some stronger modal ontological status (of the divine being) either seen to ground a weaker modal-existential status or to be incompatible with it. The aforementioned stronger status guarantees the actual existence of such a divine being. The Third Way of St. Thomas Aquinas is used as a departure point for such a general analysis. The general principle of inference is then applied to other proofs; namely, the one found in the works of J. D. Scotus.