“You’re the butcher, or you’re the cattle.”

That appears to be the theme of the fifth season of AMC’s “The Walking Dead, the most successful TV series about zombies since C-SPAN covered the Reform Party convention in 2000.

It’s a grim yet compelling drama that at times prides itself less in creative writing than in inventive ways to dispatch the ambulatory deceased. But so far, this is probably the best season since the first. It is also the darkest by far, and for the same reason: It has now dawned on the show’s heroes (and writers) that while zombies are a constant danger, humans are the real enemy.

That is because man is the only the monster there is – or ever was.

There is no shortage of exotic monsters in the imaginary bestiary of man. There are dragons, balrogs, banshees and basilisks. The problem is that they don’t exist.

And of course there was a time when we mistook real beasts for monsters, and understandably so. But we now recognize them as simple creatures simply doing what they must (though watching a cat play with a mouse sometimes gives me doubt). Sharks are terrifying, but they are not evil.

Evil requires the ability to choose good. Absent choice, evil isn’t evil, it’s just stuff that happens. If you fall into a shark tank, you are not the victim of evil. If I push you in, well, that’s a different story.

The zombies of "The Walking Dead” might as well be a metaphor for Ebola or earthquakes or meteor strikes. Birds gotta fly, fish gotta swim, zombies must feast on the flesh of the living. Only fools curse the sun for setting.

But man is something different. He is a creature with the power of moral choice, the only creature in this life with that power. That is why I loathe attempts to liken anything other than other instances of genocide to the Holocaust. Comparing it to a disease or to global warming is a moral category error that borders on Holocaust denial.

Similarly, it always bothers me when opponents of the death penalty say, “We’re talking about taking the life of a human being,” as if this hadn’t occurred to supporters of capital punishment. Of course we’re talking about a human life. If we weren’t, what would be the point?

You often hear that one shouldn’t call men “monsters,” because to do so “dehumanizes” them. This is nonsense. What makes child rapists and murderers monsters is their humanity. The Islamic State is monstrous, too. Saying so doesn’t dehumanize them. It does, however, imply that we shouldn’t spend a whole lot of time trying to reason with them.

This season of “The Walking Dead” is so good because it is finally asking the right question: What does it mean to be a human? The protagonists of the show recently encountered a group of survivors who’ve concluded that survival is the only thing that matters, and so they follow the example of zombies and start eating humans too. They rustle up their fellow men and women and turn them into cattle. When their victims plead, “You don’t have to do this,” it falls on deaf ears, just as it would if you said to a hungry polar bear, “Let’s talk about this for a minute.”

Except the victims are right. The murderers don’t have to do it. They choose to do it. And that is what makes them the only real monsters on the screen.

Originally, a monster wasn’t understood as a horrible beast. “Monster” comes from the Latin monstrum and the verb monere, meaning to warn or to instruct. A monster, technically, was an omen of evil to come. One could say that the zombies in “The Walking Dead” are true to this older understanding of the term, for they are harbingers of the evil that emerges in the living.

It’s Halloween season, and that gives me some license to talk about zombies. But the truth is that the lesson of the show is an eternal one, because the evil in men is baked-in and eternal. Forget that the capacity for evil lurks in all of us and life will find a way to remind you. This reminder can be found daily in the headlines – for those with eyes to see it.

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