Others have already addressed the concept of “selling” indulgences in this thread, so I will simply expand upon my earlier post a bit. In others words, is the concept of change in a church a bad thing (which your friend seems to imply)? As I stated before, we first have to decide whether or not we are talking about disciplines or doctrines (or something else entirely).
Doctrinal change is problematic if doctrines are considered teachings whose origins are God himself. In other words, doctrine is a manifestation of God’s Own Truth, and truth does not change. Hence, a church’s doctrines ought not change (provided that the church or denomination in question believes in the definition of doctrine that I have provided).
As Catholics, we claim that our Church has never changed any of its doctrines. Some try to prove otherwise. But the historical evidence they end up using involves either a change in discipline (i.e., a practice, and therefore not doctrinal), or an abuse committed by certain Catholics that was never outlined as a doctrine. For example, the “selling” of indulgences was simply a misdirected application of the noble practice of offering prayers and sacrifices (in this case, an offering of money) on behalf of the souls in Purgatory. The specific practice that certain priests were using to raise funds for the building of St. Peter’s Basilica was never outlined within a Church doctrine, so when the Church eventually corrected the problem it did not constitute a doctrinal change.
Plus, if a Protestant personally thinks that doctrinal change is problematic, he may be opening “a can of worms.” After all, as I pointed out in my last post, a number of Protestant denominations have made changes in things they consider to be doctrinal. If he takes issue with changes he perceives within the Catholic Church but does not take issue with the changes within his own denomination then he shows a double-standard. If it is a problem for Catholics, why is it not a problem for Protestants?
And if his point is simply to prove that we Catholics are wrong when we say that our Church has never changed any of our doctrines, the obligation is upon him to give a truthful historical account of an actual doctrinal change within the Church. The “selling” of indulgences does not do this.