You do bring up a very good question, Petrosius. And in the spirit of each of us trying to understand what the other believes or bases his/her faith in, let me try to give you an answer.
Protestantism is a very BROAD label. And I will not attempt to defend it's varied definitions. Suffice it to say that defining you as a Catholic pretty much tells us what you believe. Defining me as a Protestant will not tell you much, other than I am not a Catholic. That in itself does not define my beliefs. Catholics seem to want to lump all Protestants into one definition.
I do not base my faith in "Protestantism", for that would be such a broad statement that it would encompass many apposing beliefs. And because of this, when asked to state my religion, I always say "Christian" and if asked to explain further, I go on to say, I believe the Bible is the infallible Word of God, and the basic tenets it lays out are those in the creed that I quoted above. I believe that creed is in your Roman Catholic Catechism as well, for it is the basis of what the Bible teaches. During the Reformation, many Christians who had read and studied the words of the Bible began to understand that there were certain practices in the Roman Catholic Church that they felt were not totally biblical, some of which they felt dangerously detracted from their wish to put total, compromised faith that salvation came from Jesus Christ alone. One example: Selling indulgences did not give one forgiveness, only Grace given freely to those who professed faith in Jesus Christ brought about forgiveness of sin. There are many others.
Thus, I am not putting my salvation and daily guidance in the hands of ANY human person or organization, but rather in the hands of the Father, Son (Jesus Christ) and Holy Spirit. The "Church" means to me the "Body of Christ" and "Saints" are all true believers, and they come from various protestant denominations as well as the Roman Catholic church, though belonging to one of the above does not necessarily assure one to belong to the "Body of Christ" as there are true Christians and false Christians in all.
I choose to attend worship and teaching at a Presbyterian (PCA)church. PCA is a branch of the Presbyterian church that adheres closely to the Bible without any variation.
During the Reformation, many Christians who had read and studied the words of the Bible began to understand that there were certain practices in the Roman Catholic Church that they felt were not totally biblical, some of which they felt dangerously detracted from their wish to put total, uncompromised faith that salvation came from Jesus Christ alone.
And that is the problem. Without a living Magisterium protected by the Holy Spirit a Protestant cannot have an objective faith but only a private opinion. Nor will a simple appeal to Scripture work. The various Protestant denominations testify to the numerous conflicting opinions among them as to the meaning of Scripture. Likewise, the constant charge made against Catholics that our teachings go against Scripture will not stand since what we are arguing about are different interpretations of Scripture, as this thread highlights.
An honest Protestant must acknowledge that Catholics do indeed derive their teaching from Scripture and sincerely believe that Catholicism offers a better interpretation of it. A Protestant is free to say that this interpretation is false and that he does not share it, but he can only say that this is a matter of his opinion, not that it is a rejection of Scripture itself. It always amazes me that Protestants will rail against Catholic claims of infallibility for the Church while expressing their own private opinions as if they were the infallible interpretation of Scripture.