"matter of wisdom" is a correct and usable phrase in written English.
You can use it when referring to something that takes a great amount of sound judgement or insight. For example: "Making the right decision in this situation is a matter of wisdom."
It is a matter of practical wisdom.
We cannot think without abstractions, and it is no doubt a matter of "practical wisdom" (phronesis) to know when to construct and when to deconstruct generalizations.
As a matter of practical wisdom, it is to discipline one's actions so that others can adopt the same principles.
Whisky tasting is a matter of practical wisdom and personal experience, not theory.
Immediately after the current Prime Minister of Somalia was appointed, our older sister--Abdia Sheikh Ahmed--has publicly reminded the new PM, and all of us for that matter, the words of wisdom that our father used to utter every time he reflected and advised on the issue of leadership and the legacy that he wanted to leave for his family.
Ron Swanson's $100,000 Pyramid of Greatness Those of us who matter greatly value the meat of wisdom that is Ron Swanson.
Be Ethical: As I got older and starting working for the first time, I remember my dad on more than one occasion imparting his words of wisdom, "No matter what you do for a living, make sure you are able to sleep at night".
In earlier generations, children with the level of disabilities our son has were often institutionalized as a matter of course, the conventional wisdom being that they were too difficult to manage at home.
Only the soused Sergeant Cokes, suffering from heart problems, achieves a measure of wisdom about what matters and what doesn't, given the unpredictable coming and the unavoidable fact of death.
