This is an impossible question to answer, of course, because as Shakespeare and many others have said, the fool thinks he's wise and the wise one knows how foolish he or she is.
I am not trying to define "wisdom," just to react to something I read by Richard Rohr in his book Simplicity: Many people, he finds, already care for others and have love in their lives in various ways, but what they lack is not love but wisdom, the sense to love rightly.
Too often, he goes on, we in the Church (Rohr is a Franciscan) "have taught people to think that they're right or that they're wrong. We've either mandated things or forbidden them. But we haven't helped people to enter upon the narrow and dangerous path of true wisdom."
What he says about Christian leaders is true in many other areas. So many people think that acquiring knowledge and degrees will be sufficient. They end up forgetting the wisdom of the heart and rely entirely on logic and reason.
I can think of several people I have known who, despite their advanced degrees, are not wise parents: they do not really understand their own children from within. Being overly busy, they do not take the time to listen and see their own family members as they are, as a whole. They impose dictates, as the church does, punishing and rewarding, finding external remedies-- medications and counselors and tutors--when things do awry instead of providing loving care.
So wisdom has to do with understanding, not knowledge. It has to do with seeing the Big Picture, which is the product of maturity and reflection. People who do not learn, grow, or think are not likely to become fully human and so will never be wise. People who do not take risks and are afraid of pain will not become wise.
Aristotle is worth quoting: A wise person knows why things are as they are. He or she looks beneath the surface to the underlying person beneath the behavior pattern and comes to understand the human heart.
As I think of the writers I have encountered over the past ten years, only a few strike me as having achieved the kind of spiritual insight or wisdom that comes from contemplative living: Thomas Merton is one. Rumi is one of several mystics who come to mind, along with David Steindl-Rast, Richard Rohr, Thomas Keating, Ron Rolheiser...there are many more. These are people who understand human behavior from the inside and are able to put it into a religious or spiritual or historical context so that what they say changes lives.
The wise ones speak from the heart to the hearts of those who read them. They know, as do their students, that no one on this side of eternity can ever penetrate the mystery of things, so we remain humbly aware of our limitations, however wise others may find us.