“ We kill the criminal that society may be rid of him, and we never know whether the criminal of to-day would not have been a changed man tomorrow, and whether our punishment of him is not useless cruelty. We shut up the dangerous—as we think—member of society, but the next day this man might cease to be dangerous and his imprisonment might be for nothing. ”
 Leo Tolstoy, The Kingdom of God Is Within You (1894). copy citation

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“Besides, apologies for violence used against one's neighbor in defense of another neighbor from greater violence are always untrustworthy, because when force is used against one who has not yet carried out his evil intent, I can never know which would be greater—the evil of my act of violence or of the act I want to prevent. We kill the criminal that society may be rid of him, and we never know whether the criminal of to-day would not have been a changed man tomorrow, and whether our punishment of him is not useless cruelty. We shut up the dangerous—as we think—member of society, but the next day this man might cease to be dangerous and his imprisonment might be for nothing. I see that a man I know to be a ruffian is pursuing a young girl. I have a gun in my hand—I kill the ruffian and save the girl. But the death or the wounding of the ruffian has positively taken place, while what would have happened if this had not been I cannot know.” source