Sirius
'Some people think I'm crazy because I talk to myself all the time. The truth is I have no one else to talk to,'
He loathed this cell. He loathed every single particle that created its existence. It made him feel like an animal. Like a creature. It made him feel alone. All of his life he had been surrounded by people. People he loved. People he hated. People he tolerated. No matter who was there, there was always someone to talk with, to argue with, to debate with. Someone to talk to.
Now things had changed. He had been framed and thrown into prison for not only a crime but a crime that would have made him involved in the death of his best friend. They said he was evil. They said he was crazy. They said he was a Death Eater. He sees it in their eyes as they walk past his cell. He hears it in the screams of the people incarcerated in the accompanying cells. He tastes it in the stale air that hangs around this place like death. And he talks to himself. Oh, the sound of his voice is the one thing that assures him of his sanity. The constant reminder that this is not his fault, that it wasn't him who betrayed James and Lily, that he won't lose his mind to this hell. He was innocent.
When the guards had walked past his cell, heard him whispering his godsons name over and over like a prayer, they'd call him mad. When the Chief of Security had walked past his cell, heard him threaten to escape and kill the one who did this to him, he called him mad and ordered more Dementors around his wing. When his cousin had been dragged past him, heard his protests of innocence, she called him mad and cowardly. They all thought him mad.
But he was merely lonely. Longing for sane conversation. Longing for intelligent conversation. Longing just for plain conversation. They say talking to yourself is the first sign of madness... in fact, he was pretty sure that a mirror in his house had once told him that. He disagreed. Talking to yourself is the only way of keeping yourself company during the hardest and loneliest of times.