Gaara was not a monster, though he did kill anyone who threatened him, or annoyed him, or got in in his way. Gaara just had a different way of looking at things.
For those who don't know: Solopsism is the idea that you are the only person who exists. Everyone and everything else is just a product of your mind, and only exists in your mind. A solopsist is someone who believes in solopsism.
Everyone is the same.
Gaara had learned this from every interaction with other people. Everyone was the same, fighting for survival, fighting for their beliefs, fighting for other selfish reasons. The more Gaara looked, the more he realized that no one really cared about other people.
Gaara watched lovers from the shadows. He heard their claims that they would do anything for the other. But Gaara saw through their lies. If the the one person left the other, the person no longer fulfilled his promise. It made sense to Gaara. Once the second person no longer met the needs of the first, why should the first stay and fulfill a promise that no longer benefited him or her?
Things changed so quickly. From Gaara's objective perspective, people changed beliefs every day. One day they were willing to fight to the death for their village. The next day they muttered against the powers that ruled them. Or did they merely deceive others and not really change their beliefs?
In the end, Gaara knew it didn't matter. They didn't really exist, and Gaara could prove it. These other people only existed in his mind. With strong thoughts, Gaara's will, visible in the form of sand, reached out and erased their image from his mind.
And it was this that proved Gaara's existence to himself. Only someone who existed could have an effect on his surroundings. But Gaara could never be sure. Did he really exist? Maybe he had been formed moments before, in someone else's thoughts, complete with memories of what he thought he had done to prove his existence, but not had only been implanted in his false memories.
But Gaara was sure that no one else existed. How could real people be so shallow? How could real people do to each other the things he saw them do?
The person that called himself his father had condemned his mother to death just do gain the power of Shukaku. What sort of person would do that to anyone, let alone his own wife? And what sort of woman would bequeth such hate and bitterness to her child, as his mother had given to Gaara?
And then when Gaara grew up, his father appeared to have forgotten the reason for giving Shukaku to Gaara. Gaara wasn't an idiot. He knew that the Kazakage was the one behind the frequent assassination attempts. It was obvious, since his assassins never even bothered to hide their hitai-ate.
Even Yashamaru, the one person that Gaara had trusted, acted only for selfish reasons. Deceiving Gaara because he had been ordered to, and then trying to kill him despite Gaara's implicit trust. It was Yashamaru's attempted assassination that made Gaara see the truth.
Now he saw why these people were so shallow. Why they did contradictory things, and only cared about themselves.
They were only reflections of Gaara's mind, and so they had no minds of their own. Of course they would be simple. They were merely images that Gaara brought into existence with a thought. And so Gaara no longer felt any remorse when he killed. It was an enjoyable thing, and there was no reason not to. Gaara had created them with a thought. So he could destroy them with a thought, the same way that children built things out of blocks, only so they could knock them down.
Gaara wandered through life, content with his lot. Almost every day, he would prove to himself that he really existed, that he could affect his surroundings, when he killed someone. No illusion or phantom in someone else's mind could change its environment.
There were some things that Gaara could not destroy. Like the one who was supposed to be Shukaku. Gaara could not remove him, no matter how hard he concentrated. The constant whispers in his head were annoying, but Gaara could not destroy Shukaku with a thought. Perhaps that was a different part of his mind, and so could not be annihilated because it truly existed?
After several years, Gaara decided that he didn't care. He could just ignore the voice, and go on with his life. Even if the voice was real in a way that most people were not, it was just as petty and shallow as everyone had ever met. Maybe even more so, since its only desire seemed to be to kill everyone they met.
Just to shut it up, Gaara frequently did so, more often that he felt was necessary to prove his existence. But it didn't matter, really. It was not like Gaara could run out of people to kill. His mind was vast, and there were people everywhere.
Sometimes, Gaara wondered if he had found another truly living being. Sometimes he met people who seemed to act from motives deeper than selfishness. But each and every time, he was disappointed. When push came to shove, and it became a choice between dying and betraying a comrade, every time the person in question would choose to betray his so-called 'friend' and run for his life. Of course, they never got away, but that was beside the point. It was not like they ever had a chance against the only genuine person in all existence. They could not escape Gaara's mind, from which they had been spawned. And so they could never outdistance Gaara's reach, or run far enough to escape his judgment.
Gaara went on missions for the place he called Sunagakure, because it gave him an excuse to leave the place without disturbing the many false people who seemed to think that Gaara belonged to them, and to the village. Gaara always laughed when he heard people saying that he should be loyal to Suna and to the Kazekage. Loyal to an image? To a figment of his imagination? To a place and person that Gaara had created from his subconscious? It was absurd.
Some days, Gaara seriously considered just erasing Sunagakure. It was mostly annoying, and the illusions there were more hostile to him than enemy ninja. It was not like they could hurt him. No one could hurt him, because no one really existed. How could a shadow cause him pain? How could a mirage inflict real damage? It was foolishness, and after some time, Gaara wished that his mind were more creative. Surely it could create better playthings than these pathetic ninja types?
After some time, it became boring. Not even the world outside Suna interested him anymore. Gaara began to suspect that even the physical world was an illusion. Perhaps the only the only thing in all existence was his mind.
Gaara wasn't sure. All that he knew was that he was alone.
So it was just him against... who? No one. It was just him. The demon of Suna. Subaku no Gaara.
Just an idea I had floating around in my head for a while now. It's not a great story, but I just wanted to get it out there. I thought it would be interesting to do a story on this idea. Solopsism is a really fun philisophy to think about, because it seems too silly but can't really be disproved.
Like for the solopsist, people stop existing when the solopsist isn't thinking about them, and other people only start to exist when the solopsist thinks about them. In theory, if solopsism were true, and the solopsist had sufficient control over his mind to do so, he could kill anyone with a thought, and make anything happen. He could create another universe within the universe that is his mind, and play God over it. I just think it's a fun idea to play with.
Let me know what you thought of it. Thanks for reading!