[Note: I am not a psychologist. I know next to nothing about mental illness and have never suffered from it myself. This story deals with suicide.]

The man stepped out onto the roof. The gray clouds above were illuminated not by the moon or stars, but by the light pollution of the city below. Even on nights with few clouds, the glaring streetlights would destroy the hopes of any would-be stargazers. The man only knew vaguely that the stars were a profound absence in his life. Leaving the city to go stargazing didn’t appeal to him, though it should have.

The man stepped to the edge of the roof. This was it, he supposed. He took a deep breath, and – he heard footsteps on the concrete roof behind him. “Just enjoying the view,” he said. “Please, I’d like to be alone.” I don’t want to traumatize some poor fellow. No reason for that.

“Do you take me for an idiot?” The man’s old neighbor scolded. “Get away from the edge, come back inside with me, I’ll make some tea, and–”

“I’m sorry mister, but I’ve made up my mind. This is the right thing for me to do. Please, go away.”

“But–”

“Please, I’m familiar with the platitudes. The sayings. The ‘You have so much to live for,’s or the ‘This will hurt the people who love you’s. That doesn’t work for me. I’m a wretch that does nothing but leech of the people close to me.”

“I don’t consider you a leech.”

“I am, though. All the dinners you’ve made me, the housesitting, the tea. I can’t return anything like that. This,” he gestures toward the ledge, “is the only sort of way I could repay you.”

“Is that what you think all that was? Obligation? Or that you were an investment? I wanted to help you because I wanted to help you. And now I’m helping you again. Come on now.”

“That’s nice of you to say, but I don’t buy it. Goodbye.” The man shuffled forward a half-step, such that his toes were poking over the edge.

“If you jump, I’ll donate $10,000 to Scientology.”

The man almost unintentionally lost his balance before taking a step back and whipping around towards his neighbor. “What the hell? I didn’t think you were a part of that freakish cult.”

“I’m not. I agree with you on this, Scientology is awful and I hope that their ‘religion’ disintegrates.”

“Then why the fuck would you donate to them?”

“I don’t want you to jump. So to motivate you to stay living, I promise to make this donation that you don’t want me to make.”

“So… to keep me alive… you’re threatening me?”

“I guess you could call it that. The way I see it, you would have interpreted any positive offers – bribes, if we are being uncharitable with our language – as more evidence that you are an unwanted parasite. And the cliches I could have said would be interpreted as part of the ‘obligation’ you think I have to take care of you. By using a threat instead, I’m showing that I’m going beyond what would be considered my duty. I’ll say it again. If you jump, I’ll donate ten thousand dollars to Scientology.”

“... what the fuck.”

They stood in silence for a little while. The neighbor had a small smirk on his face, but his wrinkled brow was tight and he was clearly holding himself still to stop himself from fidgeting. The man took an absentminded step away from the ledge. The neighbor tried not to let the feeling of a small victory show on his face, but his eyes got a bit less sad. The man was too distracted to notice.

“But if I jump… then there is no reason for you to go through with … that threat of yours.” The man murmured. “You’ll keep your money, Scientology won’t get any richer, and you’ll be better off without me.”

“Are you calling me a liar who can’t keep my promises?”

“Of course not, sir! You’ve always been honest with me! But these are exceedingly strange circumstances, and I think it possible that you might lie in this situation. For example, there won’t be anyone to hold you accountable.”

“You’re trying to predict whether I’ll go through with it. That means you have a mental representation of me. In order for me to make that representation of me tell you that I’ll go through with it, I should go through with it.”

“After I’ve already jumped? Isn’t that like time travel? I’m pretty sure that’s physically impossible. Einstein or something.”

“It’s not time travel, though I understand how it can seem that way. I use a process to output what choice I make. The model you have of me in your head, if it is a good model, will use that same process. In order to achieve my goal of ‘you stay alive,’ the best thing the process can do is tell me – and by extension, the model you have of me – to go through with the promise.”

“But how do I know that your process is really… that thing you just described? Wouldn’t a better process be to tell me these things now, and if I jump, just don’t donate the money?”

“You’re thinking about it wrong again. If that’s my process, you’ll jump. That makes it an inferior process.”

“That’s just time travel, again.”

“Not really.”

“But isn’t my model of you… bad? As in, way lower quality than what is required for this time-travel scheme?”

“Again, this isn’t time travel. But your model of me is good enough, it recognizes that your model of me and the real me make decisions based off of the same process, so it would be irrational of that process to tell me to not go through with the promise.”

The pair stared at each other again.

The world split in three.

“I have no clue what you are going to do. You have thoroughly confused me. I’m done with all of this. Goodbye, friend.”

The man stepped over the edge.

The neighbor fell to his knees and cried. He’d have to sell his apartment and much of his furniture, he’d either live with the terrible secret that he’d donated to Scientology or be ostracized, and worst of all, he’d lost a friend.

Another world:
“You’d really go through with it?”

“Yep.”

“Can you even afford that?”

“Not really.”

“I guess I can’t make you do that donation.”

“I’d hope you wouldn’t.”

“I’d like to have some of that tea, then, if that’s still an offer?”

And the last world:

“I have no clue what you are going to do. You have thoroughly confused me. I’m done with all of this. Goodbye friend.”

The man stepped over the edge.

The neighbor ran to the edge in despair. As he looked down, his despair turned to relief and hope as he saw the man being pulled from a trampoline by a team of firefighters. The neighbor had stalled for long enough. The man was alive, and would hopefully, with help, decide that he would stay in this world.

But now the neighbor is scolding himself. The man had survived, but he had jumped. What was the neighbor to do now?

[Post Script: I am new at writing, so all writing advice, even super basic stuff "everyone should know" would be helpful. Thanks for reading!]