Christians believe that God has revealed himself clearly in his Word. Thus, when it comes to key historical questions (Who was Jesus? What did he say? What did he do?) or key theological questions (Who is God? What is Heaven? How does one get there?), Christians believe they have a basis on which they can claim certainty: God’s revelation. Indeed, to claim we don’t know the truth about such matters would be to deny God, and to deny his Word. (This doesn’t mean, of course, that Christians are certain about everything; but there can be certainty about these basic Christian truths).
Thus, for Christians, humility and uncertainty are not synonymous. One can be certain and humble at the same time. How? For this simple reason: Christians believe that they understand truth only because God has revealed it to them (1 Cor 1:26-30). In other words, Christians are humble because their understanding of truth is not based on their own intelligence, their own research, their own acumen. Rather, it is 100% dependent on the grace of God. Christian knowledge is a dependent knowledge. And that leads to humility (1 Cor 1:31). This obviously doesn’t mean all Christians are personally humble. But, it does mean they should be, and have adequate grounds to be.
Scripture says some negative things about doubt (Matt. 14:31, 21:21, 28:17, Acts 10:20, 11:12, Rom. 14:23, Jas. 1:6). In Matt. 14:31 and Rom. 14:23, it is the opposite of faith and therefore a sin. Further, knowing God in Scripture often seems to have a sureness about it. . . . Note especially the “certainty” of Luke 1:4, the “proofs” of Acts 1:3, and the centurion’s words of Luke 23:47. . . . If the revelation of God to which we submit is infallible, then it must serve as the criterion of all other knowledge. As such it is the standard of certitude and must be regarded as itself in some sense maximally certain.
G. K. Chesteron:
What we suffer from today is humility in the wrong place. Modesty has moved from the organ of ambition. Modesty has settled upon the organ of conviction; where it was never meant to be. A man was meant to be doubtful about himself, but undoubting about the truth; this has been exactly reversed.
Nowadays the part of a man that a man does assert is exactly the part he ought not to assert—himself. The part he doubts is exactly the part he ought not to doubt—the Divine Reason. . . . The new skeptic is so humble that he doubts if he can even learn. . . . There is a real humility typical of our time; but it so happens that it’s practically a more poisonous humility than the wildest prostrations of the ascetic. . . .
The old humility made a man doubtful about his efforts, which might make him work harder. But the new humility makes a man doubtful about his aims, which makes him stop working altogether. . . . We are on the road to producing a race of man too mentally modest to believe in the multiplication table. (Orthodoxy [reprint, San Francisco: Ignatius, 1995], 36-37.)