The Internal Witness of the Holy Spirit to the Word
Alexander Vinet (Swiss, 1797-1847): "The gospel is believed when it has ceased to be to us an external [truth] and has become an internal truth, when it has become faith in our consciousness."
John Calvin: "... the highest proof of Scripture derives in general from the fact that God in person speaks in it. The prophets and apostles do not boast either of their keenness or of anything that obtains credit for them as they speak; nor do they dwell upon rational proofs. Rather, they bring forward God’s holy name, that by it the whole world may be brought into obedience to him ... If we desire to provide in the best way for our consciences— that they may not be perpetually beset by the instability of doubt or vacillation, and that they may not also boggle at the smallest quibbles—we ought to seek our conviction in a higher place than human reasons, judgments, or conjectures, that is, in the secret testimony of the Spirit" (Institutes of the Christian Religion, 1.7.4).