The reasons for the combination of humility and wisdom are not easy to understand (and almost-certainly beyond the understanding of superficial and arrogant persons–today's all-too-common flipside of wisdom and humility–who would dismiss the combination as a mere coincidence or result of fanciful speculation by devotees). It lies in a theological problem that starts with the act of creation in Genesis, was first touched upon in the Book of Exodus, and has exercised theologians for centuries.
The book of Genesis teaches that this world is God's creation. Though the world is not a piece of God, carved out from Him as pantheists believe, it is related to God because it is His creation. Creation bears some resemblance to God; it is like God, bears some likeness to Him, or, in the words of the theologians, is analogous to God. This is especially true of humans, creatures made in His image.
It is crucial to understand that humans are analogous to God in their existnece, not through their essences–characteristics that give form to a thing. If a person is described as six-feet tall, ill-tempered, quick-witted, and a good typist, his existence is not described at all; only his characteristics are described. It would be absurd to attribute these characteristics to God through analogy (the result would be similar to the New Age religion's insistence that each individual is divine and the resulting belief that all human characteristics, no matter how passionately debased or informed by original sin, are divinely linked).
In the Book of Exodus, Moses asked God His name. God gave the puzzing reply: “I am Who Am.” The full meaning of this revelation was not fully understood until the thirteenth century, 2,500 years later, when St. Thomas Aquinas explained that God's name articulates the fundamental nature of God–He is a being that has no form, no characteristic, other than to exist. His essence is existence. His essence is simply to exist.
This is the key to understanding why the humble man becomes the wise man. We are analogous to God through our simple act of existence, not through our forms. Our forms are, in fact, can cloud our understanding of existence to the extent the forms, like greed and ambition, emanate from original sin rather than our existence as created by God. Humility strips away the forms. As a person becomes increasingly humble, he sheds the various forms that gratify the self, such as ambition and passion, because, as a humble person, he doesn't care his self.
To the extent a person sheds the forms, he becomes simpler. As the humble person sheds the forms, he increasingly becomes a being that just exists, thus making him more similar to God, a being with no forms. This, in turn, makes the humble person wise because he is more analogous to God, the source of all things and fount of wisdom.
The humble person lives daily life in a simple existence, cultivating deep understanding as he lives without the clamor of sin and self-regard that stultifies comprehension, as he lives a life as analogous to God as possible. That simple life eventually issues forth in a stream of wisdom. Earthly limitations will not stop it. A person with low intelligence–like St. John Vianney–is merely a being with the characteristic of a low intelligence quotient, but, because wisdom issues from being (not characteristics), raw intelligence becomes a secondary concern and wisdom can shine forth even in an otherwise-unintelligent person.
The humble person's daily life is analogous to a child who plays in the same countryside day-after-day. Eventually, the child knows the landscape like the back of his hand, even though he was not intentionally trying to learn it. If a group of intelligent adults gets lost in the region, the child can give them instructions, telling them of traps and explaining the best way through the terrain during that time of year.
The humble person plays in simple existence day-after-day. He is not caught-up in exercising the various forms; not caught-up in the pursuit of money and fame. He simply lives with himself without all the make-up, just looking at existence as created by God. And he thereby obtains intense wisdom as he dwells in the image of He Who knows all.
If the reader hasn't figured it out yet, I have heavy existentialist leanings. But, then again, so does creation, as pointed out in the above account of Socrates, God, and St. John Vianney.
As discussed above, God is a being who has no form, no characteristic, other than to exist, to be. His essence is existence; His act is to exist. And we imitate Him, strengthen our analogy to Him, in so far as we simply exist without the appendages of excess essences.
And it is man's essence that is stained with Original Sin. We don't know exactly how Satan tempted Adam and Eve, but we know what he tempted them with: The prospect that, if they disobeyed God, they would become like gods. Through disobedience, our first parents sought to add something to God's image, to make themselves more than beings most analogous to God by simply existing.
Before the first sin, man's forms worked harmoniously with man's existence, the forms, in a sense, obeyed man's highest attribute as a being who participates in God through the act of existence. The forms, endowed with perfect virtue, did not disrupt that participation, but rather furthered it, like a pair of legs furthers virtue today by kneeling in prayer (though the form can also act despicably, like a knee painfully kneeing a neighbor in the crotch).
But, as a result of our first parents' sin, we became fallen creatures, creatures with their goodness (our existence bestowed by God) splattered with a cancerous growth, excess essence, like water heavily doused with oil. Man's essence and existence are inextricably intertwined, and the two influence each other. After the Fall, it became tricky for existence to work with essence, for at times essence works for the good (as in kneeling or obeying or acting virtuously) at times it works for the bad (as in kneeing, disobeying, or acting despicably). The latter adds layers to the self and disrupts the self further, hurtling the individual further from simple existence. The former helps the self return to its state as a simple being approximates God through the simple act of existence.
