It is Not Enough for a Man Implicitly to Believe What He Does Not Understand

Calvin, in the Institutes, 3.2.2:

Faith rests not on ignorance, but on knowledge. And this is, indeed, knowledge not only of God but of the divine will. We do not obtain salvation either because we are prepared to embrace as true whatever the church has prescribed, or because we turn over to it the task of inquiring and knowing. But we do so when we know that God is our merciful Father, because of reconciliation effected through Christ [II Cor. 5:18-19], and that Christ has been given to us as righteousness, sanctification, and life. By this knowledge, I say, not by submission of our feeling, do we obtain entry into the Kingdom of Heaven. For when the apostle says, "With the heart a man believes unto righteousness, with the mouth makes confession unto salvation" [Rom. 10:10, cf. Vg.], he indicates that it is not enough for a man implicitly to believe what he does not understand or even investigate. But he requires explicit recognition of the divine goodness upon which our righteousness rests.