How would society, religion and the human psyche have developed if everyone was immortal and unkillable, except for the act of suicide?

One would need an ethos which lead people to take their own lives in consideration of all the others around them. Leaving aside the impossibility of the conditions you describe, the burden of immortality would make society unworkable. Even the most tolerant of attitudes would have a term.

There would be no religion. Religion only exists to offer a meager explanation for why we are here on this planet and to offer some sense of redemption for the hardship and suffering one endures on a day to day basis. Plus if everyone lived forever….it would be standing room only on this planet and reason enough to commit suicide.

The question leads me to infinite speculation of side questions, such as:

Do people still need to eat? What happens if/when they don’t?

Do people still multiply as they do in our world? What about overpopulation?

Do people still suffer from pain? Might they still use force to kill people by torturing them into suicide?

Do people still get afflictions? Diseases?

And none of it comes close, to me, to approaching answers to the questions. I certainly don’t think the changes lead to definite answers to certain changes in society, religion, or psyche – I can imagine all sorts of possibilities, but even each of those leads me into mires of considerations.

Awful idea. Among other things, it would mean that there would be no such thing as danger, no consequences for stupidity – the gene pool would get polluted with the lowest common denominator.

Worse yet, as @Zaku points out, where would everyone live? What would they eat? Would they all be healthy, or would people continue to age and sicker?

Not a great prospect.

We would be up to and beyond our a$$holes with a$$holes. Extremely amok with shmucks. People would be fed up with life and would therefore shun any continuance thereof. Garish suicides on every street corner and nobody would really notice or care.

We would perfect the agony booth to encourage people to kill themselves.

We’d probably end up with government managed suicide ages. Different for everyone depending on their socioeconomic class, of course.

@Seek are we talking Soilent Green here?

The world would be so different it would be beyond my comprehension. Overpopulation is definitely the biggest ‘problem ’ in this strange world. I doubt religion would exist. Religion is a crutch. IMO, only weak people need it. If all were invincible there wouldn’t be a need to appease the fear of mortality. That fear is what makes religion so dangerous. If you offend, or question what a person believes happens to them when they die, that fear becomes consuming. The person then usually lashes out in denile. If they’re wrong, that means they don’t really know what happens when you die. To most mortals that is a powerful and reasonable fear. Fear drives people better than anything else. I believe that the ‘comfort’ of an eternal afterlife is so powerful that it makes most religious people ignore obvious defects in their religion. And violently strike down any talk or action conflicting their beliefs.
Immortals wouldn’t have that fear driving them to ‘cling’ to a religion.
The human psyche is already so screwed up I can’t imagine how much worse it could be if allowed to fester in the mind of an immortal idiot.
This hypothetical world would be a special hell.