'matter of reflection' is a valid and usable phrase in written English.
It can be used to refer to something which one should think carefully and deeply about, or that has consequences which require deep thought. For example, "The rise of automation in the workplace is a matter of reflection, as it could potentially lead to large-scale unemployment in some industries."
So I don't know if it's a matter of reflection, I don't know that implies a kind of peaceful recognition of the situation.
Some have picked up on what Leibniz says in the quotation above ("…apperception, which is consciousness, or the reflective knowledge of this internal state") and argue that consciousness, for Leibniz, is a matter of reflection.
By contrast, stories about our relationships almost always tend to be matters of reflection, rethinking and revision.
"People who choose urban education are doing God's work," he said, "and where they choose to teach and how they choose to dedicate themselves is a matter of personal reflection".
It is never a simple matter of sheer reflection of the given social order.
Indeed, many African philosophers look far beyond the traditional philosophical texts for sources and subject matter of philosophical reflection.
However, philosophy is often viewed as more a matter of solitary reflection, perhaps involving exchanges between a few other solitary thinkers something to which the "masses" are neither privy nor attracted.
Each guest seemed to think that what he or she wound up ordering was a matter of identity, a reflection of self.
In the last few years, developments in different parts of the world, especially in the matter of food, prompt reflection on the different theories of development that have been propounded from time to time.
It is a matter of some sad reflection that on the anniversary of his death, the real hero to arise from the campus bearing his name is the chemistry professor, Syed Hamid Hussein, who drew a gun and fired on the assailants to protect his students.
"Angles of Reflection" has a matter-of-fact straightforwardness as gripping as a whodunit, but it is fundamentally a philosophical essay on mathematics.
