Teaching by Doing

I'm just starting through Noonan's book, A Church That Can and Cannot Change (2005).  So far, so good.  Early on, I came across a very interesting paragraph that I thought I'd throw out for discussion (and with a request for suggestions of further reading on this topic).  Noonan stakes out the position that we ought to be able to discern authoritative doctrine from the conduct of popes and "spiritual persons," and not just from the hierarchy's self-consciously authoritative teachings.  He says:

If we may distinguish these four large categories -- bad deeds, undefended; controversial deeds, sometimes criticized, sometimes vindicated; unchallenged practice, publicly engaged in by the popes; and conduct by spiritual persons that is unambiguously good -- we may conclude that at least the third and the fourth types of activity have a pedagogic function.  They need to be taken account of in the development of moral doctrine.

Any thoughts on this?  Any other discussions of the propriety (or impermissibility) of discerning authoritative teachings from the public (and uncontested) behavior of popes?