In general though, the scientific truth and 'human nature' don't come in conflict in the technical sense. There is an objective truth - and imo KFunk correctly states part of it. Another part of the objective truth is that most humans by nature, although peripherally attempt to seek the objective truth, are not troubled by the fact that their actions are generally not taken in reference to that objective truth.
Humans may not generally be troubled by it, but those who wish to think about it in any realistic way will have to deal with this problem sooner or later.
In regard to individual responsibility - objectively, there is no such thing, but it is a necessary fiction in human consciousness for society to not collapse on itself.
Well I think I might be saying something similar, I'm saying that even while there may not be, objectively, any means by which to claim someone has individual responsibility... by that same token there is no means to claim objectively that anyone has done an individual action.
But then what if we consider the notion of an individual to be the sum total of their genetics/upbringing, surely then we could argue that it's silly to say he doesn't have responsibility
due to his genetics/environment as that's tantamount to claiming that he doesn't have individual responsibility because of X part of the individual... Shouldn't we be personally responsible for that which we are? Surely some people need to have their freedom taken off them more than others as their limitations are more obvious (i.e. the mentally ill) but I can't yet see another defensible position that I like.
i.e. You have responsibility for all that is you and you are the product of your genetics/environment. You had no choice of what how these may have affected you, but there is no individual 'you' other than that which was created through these two forces.
Now I support legalising euthanasia for only a limited scope of terminally ill cases where the future of the patient can only deteoriate. In those cases the desire of the patient himself is probably so strong at the present point that they would almost definately commit suicide if they had the means to do so (ironically it is the cause of their pains that prevents them from doing so).
I somewhat agree with this, but I'd broaden it to the point where someone might have a less than say 25% chance of survival, especially (and perhaps to the point of allowing up to 50% chance of survival) where there will be continued complications/pain afterwards... OR something along those lines, I just don't feel comfortable saying where it can 'only' deteriorate because we're just not that good at predicting these things.
Maybe the introduction of standard contracts that are signed andd alike, to prove that the patient is consenting to being euthanased. On top of that, I would expect that the "patient" would also have to go through some sort of counseling, to make certain that - (a) they are fully aware of the decision and its consequences and (b) are "serious" (this isn't really the word I'm looking for but shit happens) about the decision.
You're thinking way too complex man
Chances are it'd need to be done by a doctor under a rigorously supervised beaurocracy, with a nurse, family/friends watching.