Since faith has been described as knowledge (notitia), assent (assensus), and confidence, or trust (fiducia), it is necessary to explain these terms and to point out their relation to one another. The following may serve to elucidate the terminology: —
a. If knowledge and assent are conceived as historic faith (fides historica), they are not really parts of saving faith; for also devils and unbelievers have both. Of historic faith, or of such a faith as merely knows, and regards as true, the “history” of Christ, Luther writes : “This is a natural work, without grace.” “Of such a faith Scripture, the Word of God, does not speak,” that is, when it treats of saving faith.
Nevertheless, while the fides historica is not a part of saving faith, it is a necessary prerequisite of saving faith, since the Holy Spirit engenders saving faith only in those hearts which know and understand the Gospel of Christ, . The so-called “implicit faith” (fides implicita, fides carbonaria) of the papists, according to which the “faithful” simply believe “what the Church teaches,” though they themselves are ignorant of the doctrine, is an absurdity; for without knowledge there can be no true faith. When Christ sent out His apostles to make believing disciples of all nations, He expressly commanded them to preach the Gospel to every creature, ; , thus showing that saving faith must be rooted in knowledge of the Gospel. The Lutheran dogmatician Scherzer writes very aptly:
“He lies who says that he believes what the Church teaches if he does not know what she teaches. For no one can believe what he does not know.”
b. However, if the term notitia is understood in the sense of true spiritual knowledge of Christ, which the Holy Ghost works through the Gospel (notitia spiritualis) and the term assensus is conceived as spiritual assent to the promises of the Gospel, which the Holy Ghost likewise works through the Gospel (assensus spiritualis), then both these terms include the fiducia cordis, or the sincere confidence of the heart in the grace of God offered in the Gospel. In other words, in that case the terms are synonymous. This fact is obvious from the Scriptural usage of the terms; for at one time it ascribes salvation to knowledge, ; ; ; , at another to assent, ; , and again to confidence, . In all these cases knowledge, assent, and confidence are synonyms of saving faith, so that each may be used without the other to describe the fiducia cordis by which a sinner is saved. The Lutheran dogmatician Buddeus rightly says:
“Knowledge without assent and assent without confidence is not that knowledge nor that assent which constitutes justifying faith.”
Luther:
“Faith is a living, bold trust in God’s grace, so certain that a man would die a thousand times for it.” .