[1]As the natural end of all proof is to give assurance, every kind of it must be considered a mean to persuade and determine the mind. Not but that there are different kinds, and that in great variety. If we refer these to their respective topics, some are _internal_ and _artificial_, others _external_ and _inartificial_; some belong to the philosopher, others to the theologian, the former having their source in nature, the latter in revelation; another sort, again, rests on _witnesses_, and another on _documents_. But if we consider their persuasive force, they may be conveniently ranged under the two classes of _probable_, and _certain_ or _demonstrative_. But if it be asked what sort of proof we have hitherto used, and drawn out to the best of our ability, we must distinguish between the _principal_ and prevailing proof, and this in form is inartificial, theological, and drawn from the inspired documents; and the proofs _occasionally inserted_ and confirmatory of the principal: these, it will be evident, are sometimes artificial and internal, such as those drawn from analogy, and the harmonious coherence of doctrines, from the unity and Catholicity of the Church, and the institution of bishops to rule particular flocks; and sometimes derived from witnesses, for such we may deem the ancient Fathers, whose importance and force, as testimonies, no prudent mind will reject. To embrace, then, the full extent of our proof, it ranges over all forms and modes, is artificial and inartificial, and rests not only on documents, but on witnesses. Now two things follow from this mixed and manifold character of our proof, of too great importance to be passed over in silence. The first of these is, the standard and criterion of resistance which our proof presents to opponents. For consisting, as it does, of so many elements, confirmed, as it is, by the absolute harmony of so many various parts, that only can be a satisfactory answer, which meets at once every particular proof, and the whole sum of it. For it would be to small purpose to give another sense, with some speciousness, to one or two points, if the great mass of matter and argument remain untouched. The only valid answer would be _to reject and deny the Primacy of supreme authority, presenting at the same time a sufficient cause for all those results of which the proof consists_. For so long as the institution of the Primacy is necessary to supply a sufficient cause for these results, so long the force of our proof remains untouched, and the institution of the Primacy unquestionable. We can therefore demand of our opponents this alternative, either to acquiesce in our proof, or, rejecting the Primacy, to find, and when they have found to establish, an hypothesis equal to the explanation of all that is contained in our arguments artificial and inartificial, in our documents and our witnesses.