When I heard this as a kid, I just thought it was some fairy tale. But this year, I made an inquiry and discovered that Ireland does not have any snakes. Immediately, I started exploring the possibility that this story might actually be based on the truth. Looking around online, I found a lot of articles debunking this story; every single one said he couldn't have driven out the snakes because there never were any snakes in Ireland. Let's look at the facts and weigh them against the counterargument.

That's about it. The fact is there is a story. I'm not saying the story is fact, only the existence of the story.

1. Ireland was covered in ice during the Ice Ages, so reptiles couldn't survive

2. Ireland is an island. There are also no snakes in Hawaii and New Zealand

Both #1 and #2 above conveniently leave England out of the picture. England, part of the Great Britain island, is literally right next to Ireland. England has snakes.

The story as told is a possibility. I'm not saying it happened, but I'm not ruling it out. I think it might be more likely that something like it did happen, since the counterarguments are so weak. If there were historical records documenting the import of snakes into England, that would weaken the case for it having happened as in the story. Also, it's difficult to imagine someone chasing snakes around. That  said, control groups are important. Scientifically speaking, England is the perfect control group. The control group has snakes, and Ireland doesn't.