One of the "proofs" Muslims offer for the rightness or superiority of Islam over other religions is that Islam is the fastest growing religion in some parts of the world. The structure of the argument is as follows:

The warrant or assumption in this argument is arguable and really needs backing (the term for arguments in support of the warrant). Clearly, Muslims need to respond to the question, "why do you believe that the fastest growing religion is the superior religion?" The answer is not obvious and necessitates a well developed argument. I have never received such an argument from a Muslim, but I invite them to produce just that. In the meantime, let me offer several reasons for doubting the warrant.

1. In the West, McDonalds, the fast-food chain, has grown rapidly. Nearly every little town has at least one set of golden arches. Granted, there is no accounting for taste; however, few individuals would confuse McDonald’s rapid growth with culinary superiority. McDonald’s has spread so rapidly because it is cheap, fast, entertaining to children, and the food, while bad and allegedly unhealthy, isn’t awful. Perhaps the same could be said for Islam.

2. When viruses spread in a host, they often initially spread very quickly and then frequently mutate to a less virulent strain. Does this indicate the superiority of a virus over the host? Yes, but merely in terms of rapid growth and adaptability. Would we, however, want to claim that the virus is ethically, spiritually, or intellectually superior to the host? This is patently absurd. The most it shows is that the virus grows well in a particular kind of host.

3. Western culture and capitalism have spread throughout the Islamic world. Does that mean that Western culture is, therefore, superior to Islamic culture? Western television, technology, music, movies, etc., are nearly ubiquitous in the Islamic world. Islamic cultures were colonized by Western cultures. Using the Muslim argument, Western culture and capitalism must be superior to the culture designed by Allah!

I could produce countless such demonstrations of how ridiculous it is to claim that rapid growth logically implies superiority.

Islam may be spreading far and wide, but so is McDonald’s, and so is AIDS! Islam, McDonald’s, and AIDS—does this prove that more is better?

You complain this was comparing apples and oranges, and in the category of religions the highest growth rate still implies truth and superiority?

In this case, a more relevant counterexample is that there are several other religions within the United States that have grown more than Islam has grown in the past 10 years. During the period from 1991-2001 (according to the World Almanac) the Muslim population in the US held its own at approximately 6 million. However, the Jehovah Witnesses grew by 26% in that time period, the Unitarians grew by 20%, and the Mormons grew by 18%. Would Muslims have us believe that within the United States the Jehovah Witness, Unitarian, and Mormon religions are the true faiths over Islam? If the Muslims are true to form, they will respond that you can’t believe the statistics produced by the Zionist controlled World Almanac. The "Christian-Zionist" conspiracy theory is frequently invoked when the numbers don’t support their claim. Oh, well...

Series: Second Thoughts On Common Islamic Assumptions
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