Ron, you're right. Sorry about the loaded question.
"I doubt we would define "severely" the same way, and I'm almost certain you mean something other than I mean when you use the word "reasoning."
I'm curoius as to what your definitions here would be? I guess I should have been more specific. By severely, I guess I meant someone who suffers from some sort of psychosis or delusions, whose perception of reality as we know it is skewed. But, when I think about it, the severely depressed person who cannot get out of bed, the agoraphobic person who cannot leave the house (or room in a group home, or what have you), the bipolar person in a manic state spending thousands a day on credit cards... they all fall into a category of what I personally consider to be people who are currently unable to care for themselves.
Would you expect someone with a shattered pelvis to go to work? Not without recovery time, and therapy, and even then they might have some limitations. I see mental illness the same way. I can't "reason" (whatever that means to you vs. what it means to me) with the depressed person to get up and take a shower because it will make them feel better. They don't care! Moving, eating, and toileting are such huge efforts for them- and I have seen patients so depressed they physically had to be toileted or fed by nursing staff. The bipolar in a manic state cannot be calmed down with mere words and logic- "How will you pay for this?" Manic people often suffer delusions of grandeur, assuming nobody will make them pay, or that they have the money, or simply being so elated they don't care. And reasoning with someone who is yelling at what we see as a parked car, but what he sees as, I don't know, "The System?" I'm sorry, but yes... until someone gives him some haldol or something to bring him down a notch, I see it as a lost cause.
"You would treat them as children, then? Not competent to determine their own destiny?"
In some cases... yeah. Do you let a person with Alzheimer's direct their own care? Do I allow my nursing home residents to lie in feces because they don't like to turn, or because, as in one Alzheimer's case I had, she thinks I am her father, and with each brief change she relives his molestation of her? No. It's painful, and difficult at times, but I step in, I make decisions for them, and I force them to have decent hygeine and care. Is it againts their nursing home rights? Yeah... but there comes a point when, as a paid caretaker... I simply have to step in and treat them like children, for their own good. Is it technically "right?" No, probably not. It's an area of ethics I have difficulty with... but sometimes, you really have to look at your patient and say "there's poop all over you. You're getting washed whether you like it or not."
I see mental illness the same way, but the good news is, mental illnesses can often be controlled or lessened in severity with medications and therapy. But... mental illness isn't cured, and people sometimes make decisions with skewed "crack cured my COPD" logic about their meds. "I feel better, I can quit taking my meds," or "I can no longer function sexually, so I'm going to quit taking my meds," or "the voices told me you are using those pills to brainwash me..." etc, etc.
When a mentally ill person is setting her house on fire to "kill the bugs," no, she is not competent to detremine her own destiny. Maybe I'm being closed minded, maybe it's a result of my personal experiences and training... but there's a reason people can be admitted to a psychiatric ward involuntarily, and a reason they keep the doors locked up their. These people are not thinking clearly, and they pose a threat to themselves or others.
Maybe it's a matter of opinion, or judgement, or whatever, but I don't believe these people should be held accountable for their actions in the same way you or I would. I have no qualms about saying that emotionally and logically, that makes sense to me.