Faith, which we affirm to be the essential kernel of Catholicism, has two sides, one which is interior and subjective, and another which comes to outward manifestation. With the heart we believe unto justification, but with the mouth confession is made unto salvation. [Footnote 30] A revealed truth {102} corresponds to supernatural faith as its necessary object. Therefore, it may be remarked in passing, the subjective act of faith is equally infallible with the divine testimony itself, upon which it is essentially based. [Footnote 31] This revealed object of faith, without which a supernatural faith is entirely inconceivable, is mediated or set forth through an organ directly instituted by God for this purpose. An individual, who thinks that he has discovered, through private investigation or in any other way, a particular point of doctrine, which hitherto has not been universally received as such, to be a revealed truth, can only make it an object of supernatural faith, when he is able to judge with certainty that this supposed new doctrine of faith would be approved by the infallible, divinely appointed organ of revealed truth. [Footnote 32] [Footnote 30: Rom. x. 10.] [Footnote 31: St. Thomas, _Secunda Secunda_, q. 1 a. 3.] [Footnote 32: Suarez, _De Fide. Disp._ iii., Sect, xiii., No. 9.] This mediating organ is, however, as we shall fully show in the course of our further exposition, no other than the Apostle Peter, and through the relation which he bears to him, his legitimate successor in office. Peter is the support and the strength of his brethren, inasmuch as _his_ faith, to which the dogmatic utterance of his successors gives a new expression according to the needs of the Church, forms a criterion for the faith of the Church. Peter, preaching of the faith, continually apprehensible through the papal definitions of faith, gives to the faith of the Church the specific form under which the same incorporates itself historically in an ecclesiastical confession. But in the Church-confession of faith, as we have before shown, its inner being comes into visible manifestation. As medium of Peter's preaching of the faith, the papacy is consequently also a Church-constitutive principle, inasmuch as through the actualization of the supreme power delegated to him by Christ, the being of the Church is made visible, and obtains an historical form. This is the sense of the words, "On this Rock I will build my Church."