No seriously, Joker is sane.
I use few words because my job takes them
I've often wondered how he reconciles that with that JLA story he wrote where the Joker was so insane, even the Martian Manhunter could only hold back his insanity for a minute or so.
Knowing Grant, he probably has some kind of explanation for it, I suppose.
I don't think the super-sanity concept literally means that the Joker is a sane person. The idea is that he's so sane that he's insane.
I've always taken issue with the fact that people seem to think insanity can be "measured" on some sort of universal, timeless scale. Like, Joker's so crazy that even cosmics identify him as such. Never mind that "insanity" is nothing more than human opinion formed by a highly varying and eternally-shifting standards.
The inhabitants of Earth, one hundred years into the future, might look back on today's Bat-comics and roll their eyes at what we consider to be "insane".
Pretty sure Joker is sane and WE are the insane ones...
Anywho, Bane is sane, as is Penguin and the Sionis Black Mask. Killer Croc is sane, but very cruel and misanthropic at best, literally sub-human at worst. Hugo Strange was sane prior to the 90s, but was pretty unstable in the 90s. Some portray Scarecrow as sane, but he's pathologically obsessed with fear, which isn't a sign of good mental health.
Going more obscure, Killer Moth and Catman strike me as pretty sane.
Also, the word "supersanity" in Arkham Asylum comes from the obviously dangerously incompetent psychiatrists who theorize that the Joker's mental state is the potential next stage in man's evolution as he tries to cope with the difficulties of modern life, the "21st century big-time multiplex man." They call it supersanity because they get so wrapped up in these big attractive ideas that they forget that they're talking about a man who may have a unique and very interesting mind, but is also incredibly dangerous.
So yeah, the Joker's "supersanity" doesn't mean he's more sane than anyone else, which doesn't even make sense really. He just doesn't fit the mold of any real mental illness, and is more in control of his actions than being "legally insane" would normally suggest. And so it's perfectly summed up in B&R #15: "I'm just differently sane." Which fits his portrayal in JLA just fine.
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