Meaning of “the humility of a charge” in “The Chief Mourner of Marne”?

Question

In "The Chief Mourner of Marne" by G. K. Chesterton, Mr. Mallow went to Father Brown to consult him about very serious problem, but he found him sitting on the floor with a serious expression, and attempting to pin the somewhat florid hat belonging to a wax doll on to the head of a teddy bear:

A new atmosphere of attention seemed to be created with the mention of the newspaper proprietor. Father Brown neither knew nor cared that his attitudes were comic or commonplace. He continued to sit on the floor, where his large head and short legs made him look very like a baby playing with toys. But there came into his great grey eyes a certain expression that has been seen in the eyes of many men in many centuries through the story of nineteen hundred years; only the men were not generally sitting on floors, but at council tables, or on the seats of chapters, or the thrones of bishops and cardinals; a far-off, watchful look, heavy with the humility of a charge too great for men. Something of that anxious and far-reaching look is found in the eyes of sailors and of those who have steered through so many storms the ship of St. Peter.

What's meant by this, especially "humility" mean "low" or "modest", so how it could be "very great"?

Answer 1

The context of the phrase here is that the phrase, "the humility of a charge too great for men", refers to the idea that someone has been given a very important task which they may not completely understand, but which they know they must complete. And so they are humble because it is the task that is great, not them. They are merely a tool being used in a great purpose.

In this case, the phrase is being used for humor because pinning the hat of a doll onto a teddy bear is not important, but Father Brown seems to be approaching it with great seriousness and concentration.

Answer 2

To offer a contrasting view to that given: the nineteen hundred years are since the time of Jesus. Father Brown is a Catholic priest, and Catholicism is a rather hierarchical faith.

The "charge too great for men", of which he is unworthy, is to speak on behalf of God and uphold his religion. With Father Brown, his comic appearance and humility sometimes disguise his devotion. He may be playing with a toy but his thoughts are on deeper things.