Is Religion an Attempt to Understand the World?

[Belacqua]

Al Posteriori reasoning is always 20/20.

I wish that this were true!

This is from Wikipedia:

The intuitive distinction between a priori and a posteriori knowledge (or justification) is best seen via examples, as below:

A priori

Consider the proposition: "If George V reigned at least four days, then he reigned more than three days". This is something that one knows a priori, because it expresses a statement that one can derive by reason alone.

A posteriori

Compare this with the proposition expressed by the sentence: "George V reigned from 1910 to 1936". This is something that (if true) one must come to know a posteriori, because it expresses an empirical fact unknowable by reason alone.

So I think it's clear that there are a huge number of a posteriori arguments which have been false. 

The fact that the sun seems to rise and set, for example, gave support to the a posteriori argument that the sun goes around the earth. 

Such arguments still require solid evidence or logical argument, and we constantly see cases where people draw wrong conclusions. Post hoc ergo propter hoc arguments, for example. 

Christianity became popular in the Roman Empire, and then the empire fell. Some have made an a posteriori case that the first of these facts caused the second, but it would take a serious look at history truly to come up with 20/20 vision on this.