One way Catholic apologists like to argue for the legitimacy of their Church is to boast about the large number of "Protestant" denominations. It is said that there are between 30,000 and 60,000 of them. In my personal experience, 40,000 seems to be the most commonly cited figure.
By far the easiest way to respond to this argument is to disarm it. If there really were 40,000 Protestant denominations (the actual number is around 1,000), that would simply make Catholicism the 40,001st Christian denomination. At least, in the eyes of the world.
And there you have your problem. In the eyes of the world. Although self-proclaimed Christians make up around 2.5 billion of the world's population, the overwhelming majority of the human race exist outside of our denominational disputes. That is why one of the most common arguments used by, for example, atheists, is also the large number of "Christian" denominations. As outsiders, they obviously do not have a bias towards the Catholic Church. They don't see in terms of Catholic vs. Protestant (and neither do I), they see in terms of Christians vs. Christians.
Catholics, by contrast, obviously do have a bias towards Catholicism. When they think in terms of Catholic vs. Protestant, what they're really thinking is "us vs. everyone who believes in some form of Jesus but is not us". Sometimes, "everyone" includes some very strange denominations indeed. But even if a Catholic apologist is wise enough to recognise that Mormons do not believe in Sola Scriptura, it is very easy to exaggerate the number of "Protestant" denominations when "Protestant" simply means "non-Catholic". But what if, for just a moment, we shift things. What if "Protestant" meant "non-Evangelical"? Well, now the Evangelicals can say "there are 40,000 Protestant denominations", and it is exactly as logical an argument for why Catholicism is heretical. That is to say, as much as I strongly disagree with the Catholic Church, not logical at all. It would be illogical if any other denomination used it, it is illogical when Catholic apologists use it.
But that doesn't solve the problem of denominations. After all, they can't all be right, can they? So although the argument is, let's be honest, rather stupid, it could at least shift the discussion. Right? Well, let's first establish what constitutes a "denomination".
As a denominational anomaly, I'm actually in a unique position in that I am not likely to argue for any denomination in particular. I'm not biased towards any of them because I find them unnecessarily divisive. I believe, as is the official position of this ministry, that there are true Christians in every denomination, but that there are no true Christian denominations. Rather, each denomination has their strengths and weaknesses. The first step to answering this dilemma, then, is to ask exactly how big these strengths and weaknesses are?
As previously mentioned, there are some very bad denominations out there. These, ironically, exist for the same reason as Catholicism. They aren't simply minor disputes over minor issues, but rather are major disputes over major issues. Mormonism, being the example we mentioned earlier, is a henotheistic religion. Henotheism (the belief in many gods with emphasis on one) is obviously an essential issue. Trinitarian monotheism is a fundamental aspect of the Christian faith. Lose Trinitarian monotheism, lose the right to call yourself Christian. Given that many Catholics hold so strongly to the doctrine of the Trinity that they practically claim they made it up, I'm sure my Catholic readers can stand arm in arm with me on that one.
Other issues, by contrast, are not so major. For example, pedobaptism, yay or nay? This, being a non-essential issue, is often a dividing line between denominations. This means that some denominations could actually be fused together and classed as one. In fact, all denominations that disagree only on "minor" issues can be fused together to form one whole Christian faith. This not only shrinks the alleged 40,000 denominations, but also makes the 1,000 denominations trivial. It is no longer about which denomination is correct, but rather which ones are "valid", by which I mean non-fatally flawed. How do we answer this?
The simplest answer is to study Scriptures. Not in a way that assumes your Church is the correct one, but in a way that assumes when God speaks, be it by word, or by the pen of a prophet, man must listen. Unfortunately for Catholics, this is where their denomination falls short, not by being one denomination in a sea of 40,000, but by being one denomination that often, and in many egregious ways, goes against the word of God, and then demands you reinterpret the word of God to agree with their disobedience.