A mistake no less common for being against the purpose of society, namely a sense of one's own security, is to allow a judge, who is the executor of the law, to be free to detain citizens, to deprive an enemy of his freedom on the slightest pretexts, and to let a friend avoid punishment in spite of the strongest evidence of guilt. Unlike every other sort of punishment, detention necessarily precedes conviction for a crime. But this peculiar characteristic does not set aside that other essential principle, which is that the law alone should determine the cases in which a man deserves to be punished. The law, therefore, should indicate what kinds of criminal evidence justify the detention of the accused, and expose him to investigation and imprisonment. Public repute, flight, confession, denunciation by an accomplice, threats, and continued hostility to the crime's victim, the circumstances of the crime, and similar evidence are sufficient proofs to imprison a citizen. But such proofs have to be established by law and not by judges, whose rulings are always contrary to public safety when they are not particular applications of general rules laid down in statute. The laws can be satisfied with ever weaker evidence for imprisonment as the punishments become more humane, as prisons become less appalling and infamous places, as compassion and humanity enter their iron gates and take control of the inflexible and hardened ministers of justice.