A Catholic writes:
First, in terms of apologetics, the sheer multiplicity of Protestant denominations and nondenominational churches undermines the claim of any to be an authentic representation of the true Church. The contrast with the unity and universality of the Catholic Church, which claims to be the Church couldn’t be starker.
1. The first problem is that Protestants don’t typically claim that any particular denomination is the “authentic representation of the true Church”. That’s something Catholics are hung up on, not Protestants. Broadly speaking, Protestants primarily care about which church or denomination is most faithful to the preaching and teaching of the Bible. Protestants don’t look to churches, then decide which is the one true church; rather, we look to the Bible, then decide which church or churches are faithful to the Bible. Of course, all this needs to be further unpacked, but that’s the fundamental point.
2. Protestants have no problem concluding which church or denomination is most biblically faithful can vary depending on time and/or place. For example, it could be the Southern Baptist denomination was the most biblically faithful, say, 100 years ago, but today the Orthodox Presbyterian Church (OPC) is the most biblically faithful. Or it could be that in Africa the most faithful denomination is the Anglican church, whereas in the US the Anglican or Episcopalian church is far from biblically faithful. Again, the most biblically faithful church or denomination can vary depending on time and/or place.
3. In addition, there could be multiple faithful churches or denominations depending on time and/or place. For example, it could be both the OPC and Reformed Baptists are biblically faithful in the United States today. As such, Reformed Baptists and Reformed Presbyterians don’t necessarily have any problem recommending one another to people seeking a church. In this case, the obvious main difference would be in whether one is a credobaptist or paedobaptist, but Reformed Baptists and Reformed Presbyterians would not break fellowship over this issue. Both Reformed Baptists and Reformed Presbyterians can and do readily acknowledge the other is faithful to the Gospel of Jesus Christ and have no problem attending one another’s churches.
4. Also, Protestants simply consider the Roman Catholic church another denomination among many. Some denominations or churches are more biblically faithful than others. As a Protestant, I would say the Roman Catholic church is a denomination with serious doctrinal errors as well as other significant problems which plague it. The Roman Catholic church is just another church or denomination among thousands of others.
5. The Roman Catholic church is in “unity” in name only, not in fact. There are significant doctrinal differences espoused within the Roman Catholic church itself. There are liberal Catholics including the current pope himself. There are or were more conservative-leaning Catholics like John Paul II and Benedict XVI. There are Catholics who think Vatican II was a serious mistake to say the very least. There are Catholics who wish to further advance the strides made in Vatican II into the 21st century. There are sedevacantist Catholics. There are Catholics like Father Weinandy who recently took issue with the current pope, then was asked by the USCCB to resign as a consultant to the bishops. In short, there is a veritable diversity of doctrinal beliefs within the Roman Catholic church, but because all are professing Roman Catholics, then the Roman Catholic church considers itself in “unity”. But again that’s a superficial “unity” at best. A “unity” in name only. Not real unity which should be unity based on doctrine and theology.