I received a good question in the combox of a prior post on sola scriptura, and the matter is important enough, I think, to warrant a post of its own.
As I pointed out in that prior post, one of the problems with sola scriptura is that the individual becomes the de facto interpretive authority, and then defines and locates "the Church" as those who agree with his own interpretation of Scripture. And this obviously leads to a multiplication of sect upon sect, as history shows.
But the objection to this argument is that the person who moves from Protestantism to Catholicism does the very same thing, essentially creates "Church" in his own image by reading the Bible and deciding that the doctrine of the Catholic Church most closely matches what the Bible teaches. So, the objection is a form of the tu quoque (i.e. you too) objection. Below I have pasted my combox response to that objection (with a few changes).
I receive this objection quite frequently. I discussed it briefly in my post titled "The alternative to painting a magisterial target around our interpretive arrow".
The gist of the objection is that in becoming Catholic I'm doing the same thing, i.e. interpreting the Bible and locating those persons who share my interpretation, and then placing myself under their authority.
But there is a very important difference. What is problematic in the Protestant approach is not that the individual uses his own intellect and will in making decisions about the identity and nature of the Church. We can't but use our own intellect and will in making decisions. Individualism is not equivalent to individual agency. So, that's not the issue.
The issue is the criterion by which we decide what is the true Church. The approach in the Protestant case (because in Protestantism "apostolic succession", insofar as the term is used, is thought to refer fundamentally to the doctrine of the Apostles) is to interpret Scripture, while typically assuming sola scriptura, and work out what one thinks was the Apostles' doctrine, and then find a present-day community of persons who shares that doctrine, call them "the Church", and then join "the Church". That very same sort of approach can, though rarely, I think, lead persons to the Catholic Church.
But if a person becomes a Catholic only because he sees that the Catholic Church shares his own interpretation of Scripture, he is not truly a Catholic at heart; he's still a Protestant at heart. One does not rightly become a Catholic on the grounds that one happens to believe (at present) all that the Church teaches; one rightly becomes a Catholic by believing (as an act of faith) all that the Church teaches (even if not fully understanding), on the ground of the sacramental authority of the Magisterium of the Catholic Church. When we are received into the Catholic Church, we say before the bishop, "I believe and profess all that the holy Catholic Church believes, teaches, and proclaims to be revealed by God." We aren't saying that we just happen to believe Catholic doctrines, i.e. we are not merely reporting our present mental state vis-à-vis Catholic doctrine. We are making a confession of faith, an act of the will whereby we are submitting to the sacramental authority of the Church regarding what it is that she "believes, teaches, and proclaims to be revealed by God" on the ground of her sacramental magisterial authority in succession from the Apostles whom Christ Himself appointed and sent.
That is why those persons who decide to wait until they agree with all Catholic doctrines before becoming Catholic are thinking like a Protestant. They're not understanding the act of faith that one makes in becoming Catholic. They are still in the mindset of 'submitting' to church authority on matters of doctrine only when they agree (or mostly agree), or picking a "church" based on whether it teaches what they already believe. They are not recognizing the sacramental authority of the Catholic Church and the difference that sort of authority makes. They are treating the Catholic Church as if it were another denomination, a Protestant "ecclesial community", without Holy Orders from the Apostles. That approach is a form of rationalism, not fides quaerens intellectum (faith seeking understanding). "Faith seeking understanding" is possible only where submission is required, but strictly speaking, submission is not required wherever the identity and nature of the Church is determined and defined by one's own interpretation of Scripture.
So what exactly is the relevant difference between the Protestant picking out a Protestant denomination that fits his own interpretation of Scripture, and the Protestant adult who becomes Catholic for the right reason? In the former case, the individual works out a set of doctrines from Scripture, and then seeks out those persons who are presently teaching according to that set of doctrines, and joins their community and submits to them. In the latter case, by contrast, the individual finds in history those whom the Apostles appointed and authorized, observes what they say about the basis of the transmission of Magisterial authority, and then traces that line of successive authorizations down through history to the present day to a living Magisterium, and then submits to what this present-day Magisterium is teaching. In both cases the individual inquirer is using his intellect and will. But in the former case he is using his own determination of *doctrine* from his interpretation of Scripture to define and locate "the Church", but in the latter case he is using the *succession of sacramental authority* from the Apostles to locate the Church and then let the Church tell him what is and is not orthodox doctrine.
"Let unity, the greatest good of all goods, be your preoccupation." - St. Ignatius of Antioch (Letter to St. Polycarp)