Batman is wrong to be nonlethal in the case of the Joker. This shows we can, in some cases, morally kill someone against his will.

I am something of a comic fan. The medium fascinates me - though not so much most of the superhero characters and stories. I am currently writing comics myself (whether they see the light of day is another question and, no, I can't draw to save a bus of orphans). However, since I am trying to be a comics creator, I'm usually interrogating comics and characters when I encounter them. Thus, I've recently become unconvinced by my favourite crime-fighter's attitude toward killing. And, specifically, killing his archenemy - who is, in fact, my favourite character in comics.

Batman and The Joker's "relationship" was best explained by Heath Ledger’s incredible portrayal of the latter, when he said in The Dark Knight:

“This is what happens when an unstoppable force meets an immovable object. You truly are incorruptible, aren't you? You won't kill me out of some misplaced sense of self-righteousness. And I won't kill you because you're just too much fun. I think you and I are destined to do this forever.”

The Joker provides us with two reasons two fierce enemies are refusing to end the life of the other. Batman is renowned not merely for his genius and being a non-superpowered superhero but also for his iron-clad principles. Principles that withstand the temptation to kill his enemies, as well as resist the lures of Gotham’s sirens (in most instances, at least). The Joker appears to be the opposite: chaotic and so loose with his principles one can almost see them dragging on the floor.

But, it seems, the two are in fact not so different. Many instances of The Joker lead readers to believe he, too, is a genius – anyone who can often stay ahead of the World’s Greatest Detective surely must be. The Joker’s ironclad principle is simply being a force of chaos and destruction. Indeed, we shouldn’t confuse the result of the principle with how the principle is held: a Rachmaninov piano solo appears chaotic, but no one disputes it requires discipline and determination to master. So it shouldn’t surprise us that neither The Joker nor Batman will kill the other.

Yet, Batman is surely mistaken in maintaining his principle of non-lethal conduct. Surely there are some good reasons, like preventing The Joker’s future crimes, where killing (against a person's will) can be a moral imperative?

I do not support the death penalty, for reasons my fellow Big Think blogger, the incredible Will Wilkinson, has already highlighted beautifully. And for this, I may appear hypocritical. Yet, my reasons against State-mandated killing are premised on the idea that there is no evidence to justify its existence: capital punishment doesn’t appear to lower or deter future crime (most murders, for example, are “crimes of passion”, which are spur of the moment reactions to sudden, unfortunate situations, not planned events in which the suspect can consider the threat of execution).