Last night some friends and I had a discussion about belief. Some argued that other people's beliefs are justification for believing something yourself. I was not one of those that argued this.

I'm essentially an empiricist. I strive to base as much of what I believe as possible on observation (both direct and indirect), logic, scientific methodology, and the observation of trusted sources.

I'm not saying that what other people believe is entirely irrelevant, or shouldn't be considered as a basis for exploring a particular set of truths. But believing something because lots of other people do is an extremely weak justification for doing so.

If there are 1.9 billion Christians in the world, and 1.1 billion Muslims, does that mean that Christianity probably has more merit than Islam? And if there are only about 14 million Jews, does that mean that both Christianity and Islam both have more merit than Judaism?

You can see the ridiculousness of weighing the relative truth of a belief system based on how many people believe it.

There was a time, not so long ago, when everybody in the world thought it was flat. Did the fact that everybody on earth believed it give the notion any more credence?

Stated simply: Judging the merits of a belief on the number of people who believe it is a very poor indicator of its truth.