My lovely girlfriend Cate is a vegetarian. For a long time, I didn’t really understand why she chose such a lifestyle, especially because she often seemed—at least to me—to really long for chicken, or even a good roast beef sandwich. I mean, Arby’s success clearly proves that every true American loves a good roast beef sandwich (and talking oven mitts).

But an incident on Thursday night has shown me why people might choose to be vegetarians.

The truth about meat is that you can never really tell where it came from. Hot dogs are the most prominent symbol of this uncertainty: you never really know what’s in a hot dog. It’s not like they print the ingredients on the package.

Because you can’t tell where the meat came from, you can’t know much about the slaughterhouse in which it was produced. Is the slaughterhouse clean? Is the meat kept safe? Upton Sinclair’s The Jungle showed us all just how dreadful those slaughterhouses can be.

This, in turn, leads to a number of ethical questions regarding the consumption of meat. Have the slaughtered animals been treated humanely? Were they fed steroids? And so on.

But I think I know the real reason vegetarians choose not to eat meat.

You never really know if you’re eating human meat or not.

Think about it: Who knows what human meat tastes like. I sure don’t. I could be eating it every time I eat meat. I could certainly be eating it sometimes when I eat meat. A lot of people go missing every day. It’s not preposterous to think that some end up in hot dogs and hamburgers and nice sirloin steaks (not that I get to eat a lot of sirloin steaks, since I’m a grad student).

The only way to be completely sure is to not eat meat. Vegetarians just figured that out before the rest of us.